Optical angular measurement system for ophthalmic applications and method for positioning of a toric intraocular lens with increased accuracy

ABSTRACT

An ophthalmic system for use in performing angular measurements in relation to a patient&#39;s eye. The ophthalmic system can include an optical angular measurement device that can provide angular indicia by, for example, projecting an image of an angular measurement reticle onto a patient&#39;s eye or by superimposing an image of an angular measurement reticle onto an image of the patient&#39;s eye. The ophthalmic system can include an optical refractive power measurement device for providing desired angular orientations for ocular implants or for incisions. The ophthalmic system can be used, for example, to align a toric intraocular lens to a desired angular orientation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/614,344, filed Nov. 6, 2009, and entitled, “OPTICAL ANGULARMEASUREMENT SYSTEM FOR OPHTHALMIC APPLICATIONS AND METHOD FORPOSITIONING OF A TORIC INTRAOCULAR LENS WITH INCREASED ACCURACY,” whichclaims priority to the following U.S. provisional patent applications:U.S. Provisional Patent Application 61/166,660, filed Apr. 3, 2009, andentitled “OPTICAL ANGULAR MEASUREMENT SYSTEM FOR OPHTHALMICAPPLICATIONS”; and U.S. Provisional Patent Application 61/112,148, filedNov. 6, 2008, and entitled “POSITIONING OF A TORIC INTRAOCULAR LENS WITHINCREASED ACCURACY.” All of the foregoing priority applications arehereby incorporated herein by reference in their entirety to beconsidered part of this specification

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention relates to ophthalmic equipment andprocedures, such as, for example, equipment and procedures forperforming cataract surgery.

2. Description of the Related Art

Certain ophthalmic procedures involve angular measurements of or on theeye. One ophthalmic procedure that generally involves angularmeasurements of the eye is a cataract surgery. Cataracts are cloudedregions that can develop in the natural crystalline lens of an eye. Acataract can range in degree from slight clouding to complete opacity.Typically, formation of cataracts in human eyes is an age-relatedprocess. If left untreated, cataracts can lead to blindness. Surgerieshave been developed for the treatment of cataracts. Typically, anincision is made in the eye and the natural crystalline lens is removed.An artificial lens called an intraocular lens (IOL) is then inserted inthe capsular bag of the eye in place of the natural crystalline lens.The spherical optical refractive power of the IOL implant may beselected, for example, so as to place the eye in a substantiallyemmetropic state when combined with the refractive power of the corneaof the eye.

A cataract surgery typically requires a phaco incision, through whichthe patient's natural crystalline lens is removed and an artificialintraocular lens (IOL) is inserted, to be made at the limbus of apatient's eye. In some cases, it may be advantageous for this phacoincision to be made along a meridian at some specified angularorientation on the eye. Thus, the angular location of the phaco incisionis measured in some way.

Cataract surgeries, and other ophthalmic procedures, may also involveadditional angular measurements. For example, a cataract surgery mayinvolve angular measurements so that the surgeon can align a toric IOLto a particular angular orientation. Toric IOL implants provide a degreeof correction for any regular astigmatism which may exist in thepatient's cornea. Such regular astigmatism results from a difference inthe degree of curvature of the cornea in orthogonal meridians such thatthe eye has different focal lengths for light incident upon it in eachof the planes of the two orthogonal meridians. Regular astigmatism hasan axis associated with it that indicates its angular orientation.

A toric IOL implant has spherical and cylindrical refractive power. Thecylindrical refractive power of the toric IOL more effectively correctscorneal astigmatism if it is accurately aligned with the angularorientation of the corneal astigmatism of the patient's eye. Therefore,there is a need for systems and methods capable of accuratelydetermining the axis of cylindrical refractive power in the cornea towhich the toric IOL implant should be aligned. In addition, there is aneed for systems and methods that allow for more accurate positioning ofthe toric IOL implant at the optimal angular orientation for correctionof the astigmatic power of the cornea.

An ophthalmic surgery may also involve Limbal Relaxing Incisions (LRI)to be performed in an effort to correct corneal astigmatism. Even oncethe desired angular locations for these incisions have been determined,the surgeon still needs some means for actually identifying the desiredangular locations on the eye. Other ophthalmic procedures may alsoinvolve certain angular measurements of the eye to be made.

SUMMARY OF THE INVENTION

In some embodiments, an ophthalmic system comprises: an opticalrefractive power measurement device for measuring at least thecylindrical power and axis of a patient's eye, the optical refractivepower measurement device having a first optical pathway along a firstoptical axis; and an optical angular measurement device in a fixedspatial relationship with the optical refractive power measurementdevice, the optical angular measurement device being configured toprovide an angular indicia for performing angular measurements oralignments with respect to the patient's eye, the optical angularmeasurement device having a second optical pathway along a secondoptical axis.

In some embodiments, a method for aligning the astigmatic axis of atoric IOL with the astigmatic axis of the cornea of a patient's eyeduring cataract surgery comprises: determining a first magnitude andaxis of the corneal astigmatism; removing the natural lens; inserting atoric IOL; deliberately misaligning the astigmatic axis of the toric IOLby at least 15° from the first astigmatic axis of the cornea; andintra-operatively measuring the total refractive power of thepseudophakic eye while the toric IOL is deliberately misaligned.

In some embodiments, a method for aligning the astigmatic axis of atoric IOL with the astigmatic axis of the cornea of a patient's eyeduring cataract surgery comprises: removing the natural lens from thepatient's eye; intra-operatively measuring the refractive power of thepatient's aphakic eye; determining the magnitude and axis of thepatient's corneal astigmatism based on the intra-operative aphakicmeasurement; inserting a toric IOL; and rotating the toric IOL so thatits astigmatic axis is aligned with the axis of the patient's cornealastigmatism.

In some embodiments, a method for aligning the astigmatic axis of atoric IOL with the astigmatic axis of the cornea of a patient's eyeduring cataract surgery comprises: removing the natural lens from thepatient's eye; inserting a toric IOL into the eye at a first angularorientation through a phaco incision; intra-operatively measuring thetotal refractive power of the patient's pseudophakic eye while the toricIOL is positioned at the first angular orientation; rotating the toricIOL to a second angular orientation prior to completion of the cataractsurgery; and intra-operatively measuring the total refractive power ofthe patient's pseudophakic eye while the toric IOL is positioned at thesecond angular orientation.

In some embodiments, a computer for use in performing cataract surgeryis programmed to perform a method comprising: electronically receiving afirst input comprising a first magnitude and astigmatic axis of a toricIOL after it has been implanted in the eye of a patient; electronicallyreceiving a second input comprising an intra-operatively measured secondmagnitude and axis of the astigmatism of a pseudophakic eye thatcomprises the toric IOL; and electronically calculating a thirdmagnitude and axis of astigmatism based on the first and second inputs.

In some embodiments, a computer for use in performing cataract surgeryis programmed to perform a method comprising: electronically receiving afirst input comprising an intra-operatively measured first magnitude andaxis of the astigmatism of a pseudophakic eye that comprises a toric IOLpositioned at a first angular orientation; electronically receiving asecond input comprising an intra-operatively measured second magnitudeand axis of the astigmatism of the pseudophakic eye with the toric IOLpositioned at a second angular orientation; and electronicallycalculating a third magnitude and axis of astigmatism based on the firstand second inputs.

In some embodiments, a method for aligning the astigmatic axis of atoric IOL with the astigmatic axis of the cornea of a patient's eyeduring cataract surgery comprises: removing the natural lens from thepatient's eye; intra-operatively measuring the refractive power of thepatient's aphakic eye; determining the magnitude and axis of thepatient's corneal astigmatism based on the intra-operative aphakicmeasurement; inserting a toric IOL; intra-operatively measuring therefractive power of the patient's pseudophakic eye; and determiningwhether the astigmatic axis of the toric IOL is correctly aligned withthe axis of the patient's corneal astigmatism based on theintraoperative pseudophakic measurement.

BRIEF DESCRIPTION OF THE DRAWINGS

For purposes of summarizing the disclosure, certain aspects, advantagesand features of the invention are described herein. Certain embodimentsare illustrated in the accompanying drawings, which are for illustrativepurposes only.

FIG. 1 includes a perspective exploded view of an embodiment of anoptical angular measurement system for projecting an image of an angularmeasurement reticle onto a patient's eye, as well as a cut-away view ofthe optical angular measurement system.

FIG. 2 illustrates an embodiment of an angular measurement reticle to beimaged onto a patient's eye using, for example, the optical angularmeasurement system of FIG. 1.

FIG. 3 is a ray trace diagram of the embodiment of the optical angularmeasurement system of FIG. 1.

FIG. 4 is a photograph of a patient's eye upon which an embodiment of anangular measurement reticle has been imaged using, for example, theoptical angular measurement system of FIG. 1.

FIG. 5 is a photograph of a patient's eye upon which another embodimentof an angular measurement reticle has been imaged using, for example,the optical angular measurement system of FIG. 1.

FIG. 6 illustrates an embodiment of an optical instrument that includesa surgical microscope and a wavefront aberrometer, the opticalinstrument being particularly suited for use by a surgeon during acataract surgery.

FIG. 7 is an optical schematic of an embodiment of the wavefrontaberrometer included with the optical instrument of FIG. 6.

FIG. 8 is a cross-sectional view of an embodiment of the wavefrontaberrometer that is schematically illustrated in FIG. 7.

FIG. 9 is an optical schematic of an embodiment of the wavefrontaberrometer of FIG. 8 having integrated therewith an optical angularmeasurement system such as, for example, the one illustrated in FIG. 1.

FIG. 10 is a perspective internal view of the wavefront aberrometer withthe integrated optical angular measurement system, as schematicallyillustrated in FIG. 9.

FIG. 11 is an optical schematic of an embodiment of the wavefrontaberrometer of FIG. 8 having integrated and optically aligned therewithan optical angular measurement system such as, for example, the oneillustrated in FIG. 1.

FIG. 12 is a ray trace diagram of an embodiment of an optical angularmeasurement system for superimposing an image of an angular measurementreticle onto an image of a patients eye that is provided by anophthalmic instrument such as, for example, the surgical microscope ofFIG. 6.

FIG. 13 is an internal side view of an embodiment of the wavefrontaberrometer of FIG. 7 having integrated and optically aligned therewithan optical angular measurement system such as, for example, the oneillustrated in FIG. 12.

FIG. 14 is a schematic plan view of a patient's cornea illustrating theproper alignment of a toric IOL.

FIG. 15 is a schematic plan view of a patient's cornea illustrating theplacement of a misaligned toric IOL.

FIG. 16 is a table illustrating the effects of misalignment of a toricIOL on the residual astigmatism of several example patients undergoingcataract surgery.

FIG. 17 is a flow chart illustrating a method for more accuratelypositioning a toric IOL during cataract surgery based on anintraoperative pseudophakic measurement.

FIG. 18 is a flow chart illustrating a method for more accuratelypositioning a toric IOL during cataract surgery by intra-operativelymeasuring the refractive power of the aphakic eye.

FIG. 19 is a flow chart illustrating a method for more accuratelypositioning a toric IOL during cataract surgery by performing at leasttwo intra-operative refractive measurements of the pseudophakic eyewhile a toric IOL is positioned at two distinct angular orientations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Various embodiments of an optical angular measurement system forprojecting an image of an angular measurement reticle, or other angularmeasurement and/or alignment indicia, onto the eye of a patient, or forsuperimposing an image of the angular measurement reticle, or otherangular measurement and/or alignment indicia, onto an image of thepatient's eye, for example, are described herein in conjunction with theaccompanying drawings. Also described herein are various methods anddevices for aligning the astigmatic axis of a toric IOL with theastigmatic axis of the cornea of a patient's eye during cataractsurgery. It should be understood that the embodiments described andillustrated herein are provided for illustrative purposes and should notbe construed as limiting. Not necessarily all described features andadvantages of the various embodiments are achieved in accordance withany one particular embodiment of the invention. Thus, the invention maybe embodied or carried out in a manner that achieves or optimizes oneadvantage or group of advantages as taught herein without necessarilyachieving other advantages as may be taught herein.

Optical Angular Measurement Systems

FIG. 1 includes a perspective exploded view 202 of an embodiment of anoptical angular measurement system 200 for projecting an image of anangular measurement reticle 208 onto a patient's eye. FIG. 1 alsoincludes a cutaway view 204 of the optical angular measurement system200. The optical angular measurement system 200 can be used, forexample, to perform angular measurements and/or alignments with respectto a patient's eye (e.g., angular measurements of, on, or in thepatient's eye). In some embodiments, the optical angular measurementsystem 200 includes a light source 206, an angular measurement reticle208, an imaging lens 210, and an output aperture 212. The opticalangular measurement system 200 may also include a mounting bracket 214for mounting the optical angular measurement system 200 to a supportstructure, or ophthalmic instrument, that fixedly supports the opticalangular measurement system 200 spatially with respect to a patient's eyesuch that an image of the angular measurement reticle 208 is projectedonto the eye. The optical components of the optical angular measurementsystem 200 may be mounted within a housing 216, such as a lens tube orthe like.

The optical angular measurement system 200 projects, for example, agraphical pattern onto the patient's eye. In some embodiments, thisgraphical pattern is an image of the angular measurement reticle 208 andis viewable by a surgeon who is performing an ophthalmic surgicalprocedure on the eye. The graphical pattern may include, for example,radial angular graduation marks that allow the surgeon to make angularmeasurements of the eye during the surgical procedure and/or to locatespecific angular positions on the surface of or in the eye, for example,for purposes of aligning surgical implants to specific angularorientations or for performing surgical acts, such as incisions, etc.

For example, the optical angular measurement system 200 can be used tomeasure the absolute angle between a first ocular feature located alonga first meridian and a second ocular feature located along a secondmeridian of the eye (e.g., the angle between two features or positionson the cornea or limbus, or between the meridians upon which they lie).It can also be advantageously used to measure or determine a relativeangle between, for example, an ocular feature and a reference point orreference meridian on the eye. The optical angular measurement system200 can be used to identify a location or meridian that is angularlyseparated by a predetermined amount from an ocular feature, referencepoint, or reference meridian (e.g., to identify a location on the corneathat is 30° clockwise from a 0° reference point on a 0°-180° horizontalreference meridian). In addition, the optical angular measurement system200 can be used to measure the angular orientation of an ophthalmicinstrument (e.g., about the instrument's optical axis) with respect tothe eye. The optical angular measurement system 200 can additionally beused for some, if not all, of the same purposes as a Mendez degreegauge.

These and other angular measurements of the eye, which can be made bythe optical angular measurement system 200, can be used for a number ofpurposes during ophthalmic procedures which include, but are not limitedto, the following: determining the appropriate angular location ororientation to make an incision (e.g., phaco incision or LRI); angularlyor rotationally aligning an ocular implant, such as a toric IOL, withinthe patient's eye to a desired angular orientation; angularly orrotationally aligning an optical instrument external to the patient'seye; determining the appropriate angular location to make an alignmentmark on the eye, etc.

In some embodiments, the projected image of the angular measurementreticle 208 allows the doctor to utilize both hands during the surgicalprocedure and may, under some circumstances, eliminate the need for ahand-held instrument, such as a Mendez degree gauge, for performing suchangular measurements. This is a significant advantage because it freesup both of the surgeon's hands to perform tasks that may have previouslybeen awkward or even impossible to perform while making angularmeasurements of the eye using a hand-held device. This facilitates thesurgeon's ability to quickly and accurately perform angular measurementsand alignments during surgery and to accurately complete a correctiveprocedure. Another advantage of the optical angular measurement system200 is that, unlike a Mendez degree gauge, it does not physically applypressure to the eye, thereby increasing the patient's comfort levelduring surgery.

In some embodiments, the light source 206 outputs monochromatic orpolychromatic visible light, though in either case it may beadvantageous for the light output by the light source 206 to have goodcontrast with the colors and features of the eye so that it is plainlyviewable on the eye. In some embodiments, the light source 206 outputswhite light, while in other embodiments it outputs red light or greenlight. In still other embodiments, the light source 206 can output othercolors. The light source 206 can output coherent or incoherent light.The light can be collimated or not. In some embodiments, the lightsource 206 is a light emitting diode (LED) or lamp, such as a halogenlamp or a xenon arc lamp. The intensity of the light output by the lightsource 206 is preferably bright enough to be clearly seen on thepatient's eye by the surgeon but not so intense as to harm the tissuesof the eye.

The light source 206 outputs light along an optical pathway generallyalong an optical axis 222 towards the angular measurement reticle 208.In some embodiments, the optical axis 222 is coincident with the visualaxis of the patient's eye when the patient is looking forward, but thisis not required. For example, in some embodiments, the optical axis 222of the optical angular measurement system 200 is laterally offset fromthe visual axis of the eye, angularly offset from the visual axis of theeye, and/or the two axes are skew to one another. In some embodiments,however, these offsets are sufficiently small so as not to appreciablyaffect the image of the angular measurement reticle 208 that is formedon the patient's eye.

The light from the light source 206 may be transmitted directly to theangular measurement reticle 208, or the optical angular measurementsystem 200 may additionally include other optical elements between thelight source 206 and the angular measurement reticle 208. For example, adiffuser may be located between the light source 206 and the angularmeasurement reticle 208 in order to more uniformly illuminate thereticle 208. In addition, in some embodiments, the optical angularmeasurement system 200 may include a lens between the diffuser and theangular measurement reticle 208 so as to, for example, image thediffuser onto the reticle. This may further improve the uniformity ofthe illumination of the reticle 208.

The light source 206 can also be a laser. The laser may output acollimated beam of light whose diameter is comparable to the diameter ofthe angular measurement reticle 208 such that the laser light fullyilluminates the reticle. In some embodiments, the light source 206 mayoutput a relatively narrow beam of laser light which then passes througha beam expander to increase the size of the beam so that it fullyilluminates the reticle 208. Other methods of illuminating the angularmeasurement reticle 208 can also be used.

In some embodiments, the angular measurement reticle 208 has generallytransparent or relatively optically transmissive portions, and generallyopaque or relatively optically absorptive portions. The angularmeasurement reticle 208 may be, for example, a sheet of opaque materialwith an optically transmissive pattern formed in or through thematerial. For example, the angular measurement reticle 208 may be asheet of opaque metal or plastic with a pattern that is physically cutout from the material such that light passes through the pattern. Insuch embodiments, one consideration is that the transmissive portion ofthe angular measurement reticle 208 be large enough to pass a sufficientamount of light to be clearly visible upon the patient's eye withoutrequiring an unduly bright light source 206.

In other embodiments, the angular measurement reticle 208 is a sheet ofgenerally optically transmissive material, such as glass or plastic,with an opaque, or relatively absorptive, pattern formed on or in thematerial. For example, the pattern may be formed by depositing an opaquecoating on the generally transmissive angular measurement reticle 208 inthe shape of the pattern, or by etching the pattern into the reticle208. In still other embodiments, the angular measurement reticle 208 canbe a generally opaque pattern suspended in air such as, for example, acircular frame to which one or more wires are attached and stretchedacross the interior void of the frame. In some embodiments, the patternformed in the angular measurement reticle 208 is centered on the opticalaxis 222 and is generally radially and/or azimuthally symmetric.

In some embodiments, the angular measurement reticle 208 is atransmissive or reflective spatial light modulator, such as a mask witha controllable mask pattern. For example, the angular measurementreticle 208 can be made up of an array of modulators that can beindividually controlled to block, pass, or reflect light, such as aliquid crystal array or display. In some embodiments, the angularmeasurement reticle 208 is communicatively coupled with a computer suchthat the computer can controllably alter various features of the angularmeasurement reticle, even during an ophthalmic procedure, by alteringthe states of the various modulators that make up the controllable maskreticle. For example, the computer can change the pattern of the reticle208, the intervals between angular graduation marks, or the orientationof an alignment indicator, among other things. In addition, oralternatively, the computer could also be linked to an opticalrefractive power measurement device (e.g., a wavefront aberrometer) soas to be able to display on the angular measurement reticle 208additional information such as the refractive power of the patient'seye, or other useful information. In addition, or alternatively, thereticle can display any type of relevant information from any othersource. In some embodiments, input to alter a controllable mask angularmeasurement reticle 208 can be provided by a surgeon via a userinterface, or automatically from some other ophthalmic device dependingupon, for example, a measurement that has been performed, the type ofophthalmic procedure, etc.

FIG. 2 illustrates an embodiment of an angular measurement reticle 208to be imaged onto a patient's eye using, for example, the opticalangular measurement system 200 of FIG. 1. In some embodiments, theangular measurement reticle 208 has a pattern that includes a pluralityof angular graduation marks 224. In some embodiments, the angulargraduation marks are arranged regularly in a complete circle from 0° to360°. In other embodiments, the angular graduation marks cover only asubset, or multiple subsets, of the 360° range. In some embodiments,angular graduation marks are formed at intervals or sub-intervals of atleast every 90°, at least every 60°, at least every 45°, at least every30°, at least every 20°, at least every 15°, at least every 10°, atleast every 5°, or at least every 1° over the angular range of thegraduation marks. The angular graduation marks may comprise, forexample, line segments, arrows, spots, or other shapes. In someembodiments, the angular measurement reticle pattern may also includealphanumeric characters, designs, logos, alignment indicators, etc.

In the case of the embodiment of the angular measurement reticle 208shown in FIG. 2, there are 36 angular graduation marks 224 arranged at10° intervals. The angular graduation marks located at 30° intervals arerepresented by longer line segments, while the intermediate 10°intervals are represented by shorter line segments. In general, however,the angular graduation marks 224 could have many different styles,depending upon, for example, aesthetic qualities or the type of surgicalprocedure being performed. While the angular graduation marks 224 shownin FIG. 2 are uniformly angularly spaced, in general, this is notrequired and the angular graduation marks 224 could instead beirregularly spaced such as, for example, by omitting angular graduationmarks at certain angles or by spacing the angular graduation atintervals of varying numbers of degrees.

The angular measurement reticle 208 may be configured so that amulti-color image of the reticle is projected upon the patient's eye.For example, the light source 206 may output white, or otherpolychromatic light. Sub-portions of the optically transmissive reticlemay include differently colored optical filters so that thepolychromatic light from the light source 206 which passes through thereticle 208 is filtered by wavelength and is ultimately imaged upon thepatient's eye in a multi-colored image. Different colors can beadvantageously used to distinguish different angular graduation marks,alignment indicators, alphanumeric information, etc.

In some embodiments, the angular measurement reticle 208 is removable toallow for installation of a replacement reticle having a differentpattern. This may be useful, for example, if certain patterns on theangular measurement reticle 208 are differently suited to the varioussurgical procedures that can be performed using the optical angularmeasurement system 200. In addition, in some embodiments the angularmeasurement reticle 208, or a portion of it, is rotatable, eithermanually or in an automated fashion using a motor or the like. Forexample, the angular measurement reticle 208 may include a first portionwith angular graduation marks 224, and a second portion with one or morealignment indicators. In some embodiments, the second portion of theangular measurement reticle 208 associated with an alignment indicatormay be rotatable with respect to the first portion of the reticle thatis associated with the angular graduation marks 224.

An angular measurement reticle 208 with a rotatable alignment mark maybe advantageous in situations where the system 200 is used in aprocedure to insert an ocular implant, such as, for example, a toricIOL. As described herein, an ocular implant such as a toric IOL isadvantageously aligned to a specific angular orientation in order toprovide good refractive correction. More about the insertion andalignment of toric IOLs is described herein. The angular measurementreticle 208 may include a rotatable alignment indicator that isdistinguishable from the angular graduation marks 224 (e.g., a linesegment or arrow of different shape, length, or color) and that can be aused as a guide for the surgeon to properly orient the ocular implant.In such cases, once the desired angular orientation of the opticalimplant has been determined, the alignment indicator can be rotated, forexample with respect to the angular graduation marks 224, so that it islocated at the desired angular orientation for the optical implant.Again, this can be done manually by the surgeon, or automatically usinga stepper motor or the like with an appropriate automated controlsystem. The surgeon can then use the alignment indicator, an image ofwhich may be projected upon the patient's eye, as a guide for correctlyorienting the ocular implant (e.g., for aligning the astigmatic axis ofa toric IOL with the axis of corneal astigmatism of the patient's eye).

In some embodiments, the optical angular measurement system 200 mayinclude other types of angular alignment guides or indicia in place ofor in addition to a reticle. For example, in some embodiments, theoptical angular measurement system uses a static or dynamic holographicoptical element (HOE) to project an angular alignment image onto thepatient's eye. In some embodiments, spinning mirrors, acousto-opticmodulators, or electro-optic modulators can be used to rapidly andrepetitively draw out an angular alignment image on the patient's eye,for example, by controllably scanning a laser beam over the eye. Instill other embodiments, one or more cylindrical lenses can besubstituted for the angular measurement reticle 208 and the focusinglenses 210. When the one or more cylindrical lenses are illuminated bythe light source 206, they will, if designed with the appropriate focallength, project one or more lines, each line corresponding to acylindrical lens, onto the surface of the patient's eye in a pattern(e.g., a radial and/or azimuthal pattern). If there are a plurality ofcylindrical lenses angularly rotated with respect to one another aboutthe optical axis 222, then the projected lines will be similarly rotatedand can serve as angular measurement indicia. Similarly, a plurality ofspherical lenses could be used in place of the angular measurementreticle 208 and the focusing lenses 210 to project a plurality of spotsonto the patient's eye in a pattern (e.g., a radial pattern) that canindicate angular measurements to the surgeon. A benefit of suchembodiments without the angular measurement reticle 208 is thatrelatively little, if any, light from the light source 206 is wasted byhaving been blocked by a reticle. Thus, it is possible that alower-power light source can be used. Other components can also be usedto create the angular measurement indicia.

In some embodiments, at least a portion of the light that is incidentupon the angular measurement reticle 208 passes through the reticle tothe imaging lens 210. The imaging lens 210 may have a single lenselement or multiple lens elements. For example, in some embodiments theimaging lens 210 includes an achromatic doublet element and oneadditional spherical lens. The lens elements can be made of manydifferent optical materials, such as various types of glass and plastic,which are known in the art. In some embodiments, the imaging lens 210may also include aspheric lens elements or other optical elementscommonly used in imaging applications.

As described herein, in some embodiments the imaging lens 210 projectsan image of the angular measurement reticle 208 onto the patient's eye.In such embodiments, the focal length of the imaging lens 210 isadvantageously set such that the angular measurement reticle 208 and thepatient's eye 220 are located at conjugate optical planes. This isillustrated in FIG. 3, which is a ray trace diagram of the embodiment ofthe optical angular measurement system of FIG. 1. The ray trace diagramillustrates the angular measurement reticle 208 and the imaging lens210. Light rays 218 from the light source 206 (not shown) that havepassed through the reticle 208 are transmitted by the imaging lens 210to the surface of the patient's eye 220. The ray trace of FIG. 3 issomewhat simplified in that the portion of the patient's eye 220 uponwhich the image of the reticle 208 is projected (e.g., the cornea) isnot actually planar. In practice, the curvature of the eye can becompensated for by providing the image of the reticle 208 formed by theimaging lens 210 with sufficient depth of focus so that the entire imageformed on the eye appears acceptably in focus. In other embodiments, itthe depth of focus is constrained, the imaging lens 210 may be designedto impart field curvature to the image that approximates the curvatureof the patient's eye.

In some embodiments, the focal length of the imaging lens 210, as wellas the distance between the imaging lens 210 and the angular measurementreticle 208, is fixed such that the image of the reticle on the eye 220can only be focused when the optical angular measurement system 200 ispositioned at the correct working distance from the patient's eye. Insuch embodiments, the optical angular measurement system 200 mayadvantageously include an alignment system for precisely determining thecorrect working distance between the angular measurement system 200 andthe patient's eye 220. One such alignment system is described in USPatent Publication 2009/0103050, entitled “OPTICAL INSTRUMENT ALIGNMENTSYSTEM,” the entire contents of which are hereby incorporated byreference herein to be considered a part of this disclosure.

In other embodiments, however, the distance between the imaging lens 210and the angular measurement reticle 208 is variable, whether by virtueof the imaging lens 210 or the angular measurement reticle 208 beingaxially adjustable, such that the image of the angular measurementreticle 208 can be projected upon the eye 220 over a range of workingdistances. For example, in some embodiments, the imaging lens 210 is azoom lens or otherwise has a variable focal length such that themagnification of the image of the reticle 208 on the eye 220 isvariable. The magnification of the imaging lens 220 could be set,whether manually or automatically, such that the image of the angularmeasurement reticle 208 on the eye 220 is about the size of thepatient's pupil, or about the size of the patient's iris, or some othersize. Different sized angular measurement images may be best-suited fordifferent surgical procedures.

FIG. 4 is a photograph of a patient's eye upon which an embodiment of anangular measurement reticle 208 is imaged using, for example, theoptical angular measurement system 200 of FIG. 1. FIG. 4 is alsorepresentative of a view provided by, for example, a surgicalmicroscope, and upon which an image of an angular measurement reticle issuperimposed. The reticle pattern in this embodiment includes acrosshair which may be aligned, for example, with the 0°-180° and90°-270° horizontal and vertical reference meridians on the patient'seye. This alignment of the crosshair to the horizontal and verticalreference meridians can be accomplished using a rotatable angularmeasurement reticle 208, or by simply rotating the optical angularmeasurement system 200 about its optical axis 222. As is evident fromthe photograph, both the patient's eye and the image of the angularmeasurement reticle 208 are visible to the surgeon. In some embodiments,the image of the angular measurement reticle 208 is transverselycentered on the pupil of the patient's eye, or on the patient's visualaxis (which may not necessarily coincide with the center of the pupil).This can be accomplished using an alignment system such as the onedescribed in US Patent Publication 2009/0103050.

FIG. 5 is a second photograph of a patient's eye upon which anotherembodiment of an angular measurement reticle is imaged using, forexample, the optical angular measurement system of FIG. 1. FIG. 5 islikewise also representative of a view provided by, for example, asurgical microscope, and upon which an image of an angular measurementreticle is superimposed. The reticle pattern in FIG. 5 is yet another ofthe many possible reticle patterns that could be used. This particularpattern includes a central circular shape with an indented wedge. Insome embodiments, the wedge is advantageously aligned with either the0°-180° reference meridian of the eye or the 90°-270° referencemeridian.

In some embodiments, the optical angular measurement system 200 isadvantageously integrated with another ophthalmic system, such as, forexample, a surgical microscope and/or an optical system for measuringthe refractive power of a patient's eye, such as a wavefrontaberrometer. For example, in some embodiments, the optical angularmeasurement system 200 is integrated with the surgicalmicroscope/wavefront aberrometer instrument described in US PatentPublications 2005/0243276 and 2005/0241653, both entitled “INTEGRATEDSURGICAL MICROSCOPE AND WAVEFRONT SENSOR,” the entire contents of bothof which are hereby incorporated by reference herein to be considered apart of this disclosure.

FIG. 6 illustrates an embodiment of an optical instrument that includesa stereoscopic surgical microscope and a wavefront aberrometer, orsensor, the optical instrument being particularly suited for use by asurgeon during a cataract surgery. The optical instrument 710 includes asurgical microscope 712, or other suitable viewing device (e.g., onethat provides a three-dimensional view), attached to a wavefront sensor714, or other optical refractive power measurement device for measuring,for example, the spherical power of a patient's eye and/or thecylindrical power and axis of the eye. In some embodiments, thewavefront aberrometer is mounted onto the surgical microscope such thatthe angular relationship between the wavefront aberrometer and surgicalmicroscope, for example, about their common optical axis, is knownand/or fixed. In some embodiments, this angular relationship is suchthat, for example, horizontal and vertical lines, or other indicia, ofan eyepiece reticle within the surgical microscope are aligned withhorizontal and vertical lines, or other indicia, of an angularmeasurement reticle (e.g., 208) within an optical angular measurementsystem (e.g., 200) mounted to the wavefront aberrometer, as describedherein.

In some embodiments, wavefront aberrometer includes one or morefasteners for removably attaching the wavefront aberrometer to thesurgical microscope. In some embodiments the wavefront aberrometer isremovably attached to the surgical microscope and a spatial relationshipto one another such that the two devices are optically aligned. Forexample, their respective optical axes are co-linear for at least aportion of their length.

The surgical microscope 712 includes an eyepiece 716, or other viewingmechanism for allowing a doctor to view an eye 720 of a patient. Thesurgical microscope 712 includes a light source 722 for providingvisible light into the optical pathway of the eyepiece 716, a focusingknob 724 for adjusting the focus of the microscope 712, and an objectivelens 726, or other suitable lens, for focusing light beams. The surgicalmicroscope may also include a support structure for movably supportingthe surgical microscope over a patient in a supine position.

FIG. 7 is an optical schematic of an embodiment of the wavefrontaberrometer 714 included with the optical instrument of FIG. 6. Thewavefront aberrometer 714 is a Talbot-Moiré wavefront aberrometer and isdescribed in more detail in U.S. Pat. No. 6,736,510, entitled“OPHTHALMIC TALBOT-MOIRÉ WAVEFRONT SENSOR,” the entirety of which ishereby incorporated by reference herein to be considered a part of thisdisclosure. The Talbot-moiré wavefront aberrometer is advantageous insome embodiments because it has a large dynamic range suitable fortaking phakic, pseudophakic, and aphakic refractive power measurementsof a wide range of individuals. Other types of wavefront aberrometers,other types of instruments for performing refractive power measurementsof the eye, can also be used, however. For example, a Shack-Hartmannwavefront aberrometer can be used in some embodiments. In the case ofthe Talbot-Moiré aberrometer illustrated in FIG. 7, a light source, suchas a laser 810 sends a narrow collimated beam of light 812, less thanthe diameter of the pupil of the eye, usually less than about 1 mm indiameter, to reflect from a beam splitter 814. The beam of light 812enters the eye 816 through the pupil 817 where it is focused to a point820 on the retina 818.

The light is reflected from the retina 818 where it passes through aseries of relay lenses 822, 824. The light then passes through one ormore reticles 826, 828, creating a shadow pattern. A CCD (charge coupleddevice) camera 830 records the shadow pattern formed by reticles 826,828. The shadow pattern can be analyzed to determine informationregarding the optical aberrations of the patient's eye, includingdefocus, astigmatic power, and astigmatic axis.

FIG. 8 is a cross-sectional view of the wavefront aberrometer, orsensor, 714 that is schematically illustrated in FIG. 7. In particular,the interior of one embodiment of the wavefront sensor 714 isillustrated. As described herein, the wavefront sensor 714 includes alaser source 810 for creating a beam of light. In some embodiments, thebeam of light has a wavelength in the infrared portion of the spectrum.During operation, the beam of infrared light is directed by a mirror 942toward a beam splitter 814 or other suitable device. An combiningoptical element, such as a combiner mirror 746 (e.g., a dichroicmirror), a beam-splitter, or other similar device, reflects the beam ofinfrared light down into the eye of the patient. The combiner mirror 746preferably reflects the light from the wavefront aberrometer laser 810while transmitting at least a portion of visible light through anoptical passageway that passes through the wavefront aberrometer housing(e.g., the wavefront aberrometer housing may include windows locatedopposite one another on opposing surfaces to allow visible light to passthrough the housing, via, for example, the combiner mirror 746, 2 thesurgical microscope) to the surgical microscope so that a surgeon cansee the patient's eye while looking through the combiner mirror 746using the surgical microscope 710.

After the infrared light beam enters the eye, it is reflected, as awavefront, from the retina of the eye toward the combiner mirror 746.The combiner mirror 746 redirects the light beam through the beamsplitter 814 toward the first lens 822. The first lens 822 relays theinfrared light beam off of mirrors 950 and 952 toward the second lens824, which directs the light beam onto the first reticle or grating 826.The light beam is diffracted by the first grating 826 and then travelsthrough the second grating 828, which further diffracts the light beamand creates a final image of the wavefront reflected from the eye, whichis captured by the camera 830.

A surgeon 105 can use the surgical microscope 712 to examine the eye 125of the patient during a surgical procedure. Visible light reflectingfrom the patient's eye travels along the optical axis of the surgicalmicroscope 712 and the wavefront aberrometer 714 and passes through thecombiner mirror 746 into the surgical microscope 712. The wavefrontaberrometer 714 and the surgical microscope 712 can allow the surgeon todirectly view the patient's eye while the wavefront aberrometer 714simultaneously performs measurements of the refractive characteristicsof the patient's eye. As a result, a surgeon can view the results of agiven step of a surgical procedure without having to move the patient,the patient's eye, or the device.

FIG. 9 is an optical schematic of an embodiment of the wavefrontaberrometer 714 of FIG. 7 having integrated therewith an optical angularmeasurement system such as, for example, the one illustrated in FIG. 1(e.g., optical angular measurement system 200). The optical schematic ofFIG. 9 shows the wavefront aberrometer 714 and its constituentcomponents substantially as shown in FIG. 7. However, the opticalangular measurement system 200 is also included. The wavefrontaberrometer 714 is aligned with the patient's eye along a first opticalaxis 832, while the optical angular measurement system 200 is alignedwith the patient's eye along a second optical axis 222. In someembodiments, the optical axes 832, 222 are coplanar but are angularlyseparated and intersect one another in the vicinity of the patient's eye(e.g., at the cornea proximal to its center).

While the optical angular measurement system 200 of FIG. 9 is orientedat an angle with respect to the patient's visual axis (while lookinggenerally straight forward), in some embodiments, the angle issufficiently small so that the image of the angular measurement reticle208 that is projected onto the eye is not distorted in a clinicallysignificant way. For example, in some embodiments the optical angularmeasurement system 200 is oriented at an angle of less than 20°, lessthan 15°, less than 10°, or less than 5° with respect to the patient'svisual axis (while looking generally straight forward) and/or theoptical axis 832 of the wavefront aberrometer.

FIG. 10 is a perspective internal view of the wavefront aberrometer 714with the integrated optical angular measurement system (e.g., 200), asschematically illustrated in FIG. 9. In some embodiments, the opticalangular measurement system 200 is mounted within the housing of thewavefront aberrometer 714 using the mounting bracket 214. The mountingbracket 214 can be adapted to provide a desired angle between theoptical axes 222, 832 of the optical angular measurement system 200 andwavefront aberrometer 714, respectively, when mounted to a wall or othersupport structure of the wavefront aberrometer 714. In some embodiments,since the optical angular measurement system 200 is fixedly connected tothe wavefront aberrometer 714 (which may in turn be mounted on thesurgical microscope 712), the optical angular measurement system 200 canbe used to angularly align the wavefront aberrometer 714 and/or thesurgical microscope 712 (e.g., about their shared optical axis 832) to adesired angular orientation with respect to the patient's eye. Theoptical angular measurement system 200 can also be used to angularlyalign the wavefront aberrometer 714 with the surgical microscope (if,for example, these units are rotatably mounted to one another) byaligning the image of the angular measurement reticle 208 with, forexample, a patterned reticle provided in the surgical microscope (e.g.,at an internal focal point within the microscope).

In some embodiments, the optical angular measurement system is fixedlymounted with respect to the wavefront aberrometer such that, forexample, vertical and horizontal meridian indicia provided by theangular measurement system are aligned with the vertical and horizontalaxes of the optical refractive power measurement device. This can beadvantageous since it helps to ensure that, for example, a particularcylindrical power axis of a patient's eye measured by the opticalrefractive power measurement device coincides with the correspondingangle indicated by the angular indicia from the optical angularmeasurement device. For example, if the optical refractive powermeasurement device were to measure that a patient's astigmatic axis islocated at 37°, then the fixed alignment between the optical refractivepower measurement device and the optical angular measurement devicewould help to ensure that the 37° angle measured by the opticalrefractive power measurement device coincides with a 37° markingprovided by the optical angular measurement device.

In the case of the wavefront aberrometer described herein, in someembodiments, the angular measurement system is fixedly mounted to thewavefront aberrometer such that vertical and horizontal meridian indiciaprovided by, for example, markings on an angular measurement reticle arealigned with vertical and horizontal axes of a CCD camera that is usedto detect optical wavefronts and measure therefrom the cylindrical powerand axis of a patient's eye.

Fixed alignment between, for example, the wavefront aberrometer and anoptical angular measurement device may be particularly advantageous inthe case where the wavefront aberrometer is a removable attachment to asurgical microscope, as described herein. In particular, if the opticalangular measurement device were instead fixed to the surgicalmicroscope, then it could be difficult to properly align the angularindicia provided by the optical angular measurement device to the axesof the wavefront aberrometer after repeatedly being attached to, anddetached from, the surgical microscope. This could lead to discrepanciesbetween angles measured by the wavefront aberrometer and thecorresponding angles indicated by the angular indicia provided by theoptical angular measurement device.

The housing and componentry layout of the wavefront aberrometer 714 inFIG. 10 is similar to what is illustrated in FIG. 8. However, whereasthe wavefront aberrometer 714 illustrated in FIG. 8 has a single bottomwindow 754 through which light from the aberrometer 714 and the surgicalmicroscope 712 enters and exits the unit (in addition to a top windowfacing the surgical microscope), the wavefront aberrometer 714illustrated in FIG. 10 has an additional bottom window 1010 at whichlight from the integrated optical angular measurement system 200 exitstowards the patient's eye. Also illustrated in FIG. 10 are both theoptical axis 222 of the optical angular measurement system 200 and theshared optical axis 832 of the wavefront aberrometer 714 and thesurgical microscope 712.

FIG. 11 is an optical schematic of an embodiment of the wavefrontaberrometer of FIG. 7 having integrated and optically aligned therewithan optical angular measurement system such as, for example, the oneillustrated in FIG. 1. The optical schematic of FIG. 11 shows thewavefront aberrometer 714 and its constituent components substantiallyas shown in FIG. 7. However, the optical angular measurement system 200is also included. In the embodiment of FIG. 11, the optical angularmeasurement system 200 is optically aligned with the wavefrontaberrometer 714 such that both instruments share a common optical axis222, 832. This can be accomplished by providing a second beam splitter815 along the optical axis 832 of the wavefront aberrometer 714 tocombine light from the imaging lens 210 of the optical angularmeasurement system 200 with the light from the wavefront aberrometer714. In this way, the wavefront aberrometer 714, surgical microscope712, and the optical angular measurement system 200 can be opticallyaligned with respect to a shared optical axis.

FIG. 12 is a ray trace diagram of an embodiment of an optical system forsuperimposing an image of an angular measurement reticle onto an imageof a patient's eye that is provided by an ophthalmic instrument such as,for example, the surgical microscope of FIG. 6. As described herein,FIG. 1 illustrates an embodiment (200) of the optical angularmeasurement system that projects an image of an angular measurementreticle 208 onto the patient's eye. The projected image of the angularmeasurement reticle 208 in such embodiments is visible to the surgeonboth when viewing the patient's eye through the surgical microscope 212and with the naked eye independent of the surgical microscope or otheroptical instruments. In contrast, FIG. 12 illustrates an embodiment(1200) of the optical angular measurement system in which an image ofthe angular measurement reticle is instead superimposed upon the imageof the patient's eye that is provided by the surgical microscope 712,though it could alternatively be superimposed on an image from someother type of instrument (e.g., the reticle image can be superimposed bycomputer software on a camera image of the patient's eye, in this orother embodiments). In such embodiments, the image of the angularmeasurement reticle is only visible to the surgeon when viewing thepatient's eye through the surgical microscope 712. Many of the featuresthat have been disclosed with respect to the projection embodiment(e.g., 200) of the optical angular measurement system can be equallyapplied to or used with the superimposition embodiment (e.g., 1200) ofthe optical angular measurement system.

The optical angular measurement system 1200 includes a light source (notshown) that illuminates an angular measurement reticle 1208, forexample, in a manner similar to what has been described with respect tothe optical angular measurement system 200 illustrated in FIG. 1. Theangular measurement reticle 1208 is likewise similar to what has beendescribed with respect to the optical angular measurement system 200 ofFIG. 1. The optical angular measurement system 1200 may additionallyinclude an optional mirror 1240 that can be used to fold the opticalpath of the optical angular measurement system 1200 into a more compactspace, as well as an optional lens 1242 for adjusting the apparentdistance of the angular measurement reticle 1208 from the surgicalmicroscope 712.

In some embodiments, the optical angular measurement system 1200 isfixedly mounted relative to a surgical viewing device such as, forexample, the surgical microscope 712 at a position where light from theoptical angular measurement system 1200 can be combined with the opticalpath of the surgical viewing device using a combining optical element,such as a beam splitter, dichroic combiner mirror, etc. For example, insome embodiments, the optical angular measurement system 1200 is mountedon the opposite side of the combiner mirror 746 from the wavefrontaberrometer 714.

In some embodiments, the combiner mirror 746 is adapted so that it isreflective to the light used by the optical angular measurement system1200 while still transmitting at least a portion of visible light fromthe eye to the surgical microscope. Thus, light from the optical angularmeasurement system 1200 that is incident upon the combiner mirror 746 isreflected toward the objective lens 726 of the surgical microscope 712.This can be accomplished by, for example, forming an optical layer onthe combiner mirror 746 to act as a spectral notch reflector over thewavelength band of light used by the optical angular measurement system1200. In some embodiments, the width of the spectral notch is made smallenough to avoid appreciably interfering with the image provided to thesurgeon by the surgical microscope. In some embodiments, the opticalangular measurement system 1200 is configured to operate at awavelength, or range of wavelengths, such as long red wavelengths,though other wavelengths are also possible. It should be appreciatedthat there are also other ways of configuring the combiner mirror 746 toreflect light used by the optical angular measurement system while stilltransmitting sufficient visible light to the surgical microscope fromthe eye to provide an accurate image of the eye. Alternatively, otherarchitectures can be used where optical pathways from the surgicalmicroscope and the optical angular measurement system are combined usingmultiple combiner optical elements.

In some embodiments, the surgical microscope and the optical angularmeasurement system 1200 are configured such that the surgical microscopeimages the angular measurement reticle 1208 while simultaneously imagingthe patient's eye. For example, the angular measurement reticle 1208 canbe located at an object plane (e.g., a plane that is conjugate to theimage plane of the microscope) of the surgical microscope.

In some embodiments, the angular measurement reticle 1208 is positionedthe same optical path distance away from the objective lens 726 of thesurgical microscope as the patient's eye 220. In such embodiments, theoptional lens 1242 of the optical angular measurement system 1200 can beforegone since the angular measurement reticle 1208 and the patient'seye 220 will both be simultaneously focused by the surgical microscope712, for example, when the instrument is located at its intended workingdistance from the patient's eye.

In some embodiments, however, it may be beneficial to set the angularmeasurement reticle 1208 at a different optical path distance from theobjective lens 726 of the surgical microscope than a patient's eye 220.For example, in some embodiments, it may be desirable to make theoptical angular measurement system 1200 more compact by shortening thisdistance. In other embodiments, a longer path distance may be desirable.However, in either case a lens 1242 can be provided along the opticalpath of the system 1200 between the angular measurement reticle 1208 andthe objective lens 726 of the surgical microscope to adjust the apparentdistance between the objective lens 726 of the surgical microscope andthe angular measurement reticle 1208 to match the actual distancebetween the objective lens 726 and the patient's eye 220, for example,when the instrument is located at the intended vertical working distanceabove the patient's eye. In this way, the angular measurement reticle1208 and the patient's eye at 220 can both be simultaneously imaged bythe surgical microscope despite differences in the optical path lengthfrom the objective lens 726 to each of these planes.

In some embodiments, the apparent distance between the angularmeasurement reticle 1208 and the surgical microscope is variable by wayof, for example, a zoom lens or axial movement of the reticle. In thisway, the instrument can operate at a variety of working distances whilethe surgical microscope still clearly images the angular measurementreticle.

FIG. 13 is an internal side view of an embodiment of the wavefrontaberrometer of FIG. 7 having integrated and optically aligned therewithan optical reticle superposition system such as, for example, the oneillustrated in FIG. 12. The optical angular measurement system 1200 isillustrated on the left-hand side of the combiner mirror 746, while thewavefront aberrometer 714 is illustrated on the right-hand side of thecombiner mirror. The light source 1206 of the optical angularmeasurement system 1200 illuminates the angular measurement reticle1208. The light is transmitted via the reticle 1208 is incident upon thecombiner mirror 746, which directs the light into the surgicalmicroscope 712.

In some embodiments, an optical angular measurement device can be alaser line projector that can be integrated and optically aligned with,for example, a wavefront aberrometer, or other refractive measurementdevice, that is mounted on the surgical microscope. Such a laser linecan serve as one type of alignment indicator for showing, for example,the angular axis to which the astigmatic axis of a toric IOL should bealigned, as described herein

The laser line projector may include a laser source that is alignedwith, for example, the optical axis that is shared by the wavefrontaberrometer and the surgical microscope. This can be done using a beamsplitter or other combining optical element to combine a visible laserbeam from the laser source with the light from the wavefront aberrometerand/or the surgical microscope. The laser source can be incident upon,for example, a rotating mirror located, for example, between the lasersource and the beam splitter. This rotating mirror can be rotatableabout the optical axis of the instrument, and about an axis that isorthogonal to the optical axis of the instrument. Rotation of the mirrorabout the axis that is orthogonal to the optical axis of the instrumentat a high speed can create the appearance of a laser line that isprojected onto the patient's eye.

The mirror can be rotated about the optical axis of the instrument inorder to specify the orientation of the projected laser line. This canbe done, for example, manually by the surgeon based on angulargradations marked on the laser line projector, or automatically using astepper motor or other actuator based on a signal from the computerindicating the appropriate amount and direction of rotation of the toricIOL. In some embodiments, the orientation of the laser line projector isdetermined based on an angle and direction of rotation relative to theorientation of the instrument at the time the total refractivemeasurement of the pseudophakic eye is taken. The mirror can be rotatedabout the optical axis of the instrument to an orientation thatcoincides with, for example, the axis to which the toric IOL should bealigned (i.e., the calculated astigmatic axis of the cornea). Thisvisible indicia allows the surgeon to easily and conveniently view thecalculated astigmatic axis of the cornea while viewing the tonic IOLthrough the surgical microscope.

In some embodiments, the indicia of the axis to which the toric IOLshould be aligned is determined by a rotatable reticle that is projectedonto the eye or viewable by the surgeon through the surgical microscope.For example, in the case of the wavefront aberrometer mounted to asurgical microscope, as described herein, the light from the wavefrontaberrometer and the surgical microscope can be combined using a beamsplitter. In some embodiments, a reticle is positioned on the side ofthis beam splitter opposite from the wavefront aberrometer. Thus, thebeam splitter can be used to pass light reflecting off of the reticle,or transmitted through the reticle, to the surgical microscope so thatthe reticle is viewable by the surgeon through the surgical microscope.For example, the reticle may appear superimposed upon the image viewedthrough the microscope. Other arrangements for achieving this effect arealso possible.

The reticle can, for example, be positioned at a distance from the beamsplitter that is substantially equal to the intended working distancebetween the beam splitter and the corneal apex of the patient's eye sothat the reticle can be viewed through the surgical microscope in focus.The reticle can include a mark to indicate the intended axis ofalignment for the tonic IOL (i.e., the calculated axis of cornealastigmatism). The reticle can also be rotatable so as to properly orientthe mark on the reticle at the astigmatic axis of the cornea. Thereticle can be, for example, manually rotatable based on angulargradations provided on the reticle housing, or automatically rotatableby a motor or other actuator based on a signal from the computerindicating the appropriate amount and direction of rotation of the toricIOL. In some embodiments, the orientation of the laser line projector isdetermined based on an angle and direction of rotation relative to theorientation of the instrument at the time the total refractivemeasurement of the pseudophakic eye is taken. In some embodiments, anoptical angular measurement device, an optical refractive powermeasurement device (e.g., a wavefront aberrometer), and/or a surgicalmicroscope are communicatively coupled to a computer. In someembodiments, the computer can be used to process measurement data fromthe optical refractive power measurement device (e.g., wavefront data)in order to determine, for example, the spherical power of the patient'seye and/or the cylindrical power and axis. Based on these measurements,for example, the computer can determine (e.g., calculate) an alignmentvalue. Alternatively, or in addition, the alignment value could beprovided by the surgeon via a user interface.

The alignment value can indicate the angular orientation to which theastigmatic axis of a toric IOL should be aligned. This can bedetermined, for example, from pseudophakic and/or aphakic measurementsof the refractive power of the patient's eye intra operatively during,for example, a cataract surgery, as described herein. The alignmentvalue could also indicate a desired angular orientation of some othertype of ocular implant. In addition, the alignment value can indicatethe angular location where some surgical action should be performed,such as an incision (e.g., a phaco incision or a limbal relaxingincision).

The computer can then control the optical angular measurement device toadjust some aspect of the angular indicia based on the alignment value.For example, the computer could control the angular orientation of analignment indicator. The alignment indicator could be a marking on anangular measurement reticle, a laser line, or other mark, projected ontothe eye, etc. Other types of alignment indicators can also be used. Inthis way, the computer can provide an automated indication to a surgeonof a particular angular orientation to be used during the surgicalprocedure. Other aspects of the angular indicia, in addition to theangular orientation of an alignment indicator, can also be controlledbased on input from another optical device, such as a wavefrontaberrometer, or user input. These include, for example, the shape, size,pattern, design, information content, etc. of the angular indicia.

In some embodiments, the angular indicia provided by an optical angularmeasurement device can be made switchable between “on” and “off” states,while still allowing substantially full operation of the surgicalmicroscope and/or optical refractive power measurement device. Theon/off state of the angular indicia can be controlled based on userinput through a user interface, or automatically based on input fromanother device. This can be advantageous by allowing angular indicia tobe switched on when it is needed to make an angular measurement or toperform an angular alignment, for example, while allowing the angularindicia to be switched off when it is not needed, when it may bedistracting to the surgeon, or when it would interfere with theoperation of, for example, the optical refractive power measurementdevice or the surgical microscope.

The angular indicia provided by optical angular measurement devicesdescribed herein can be made switchable between on and off states by,for example, configuring the respective light sources used by theoptical angular measurement devices to be switchable on and off.Alternatively, or in addition, a controllable shutter can be used tocontrollably block or pass light from an optical angular measurementdevice, thereby effectively switching the angular indicia off or on. Forexample, with reference to the embodiment illustrated in FIG. 10, acontrollable shutter could be placed over the window 1010 or at anappropriate position within the lens tube 216 in order to prevent animage of the angular measurement reticle from being projected onto thepatient's eye. With respect to the embodiment illustrated in FIG. 12, acontrollable shutter could be placed in a position, for example, at aposition before the combiner mirror 746 in order to prevent light fromthe optical angular measurement device from being transmitted to thesurgical microscope. This is in contrast to an angular measurementreticle provided within a surgical microscope (e.g., within an ocular,etc. of the surgical microscope), which generally cannot be disabledwithout also disabling the surgical microscope itself even thoughangular indicia may not always be necessary and, in fact, may even bedistracting in certain circumstances. Thus, in some embodiments, it isadvantageous that the surgical microscope and the optical angularmeasurement device, despite being optically aligned, havenon-fully-overlapping optical pathways, that allow the angular indiciato be selectively disabled without disabling the surgical microscope, asdescribed herein. In some embodiments, it is likewise advantageous thatthe wavefront aberrometer, or other optical refractive power measurementdevice, and the angular measurement device, despite being opticallyaligned, each has an optical pathway, at least a portion of which is notshared by the other. Other techniques for configuring an optical angularmeasurement device to be switchable on and off can also be used.

Positioning of a Tonic Intraocular Lens

In some embodiments, in order to select and properly align a toric IOLto a desired angular axis so as to correct the cylindrical refractivepower of the cornea of a patient's eye during cataract surgery, the axisand magnitude of the cylindrical power of the cornea are firstdetermined. Since the crystalline lens is to be removed during thecataract surgery, it is desirable to obtain measurements of thespherical and cylindrical refractive power that are attributable solelyto the cornea. Refractive measurements obtained by certain otherinstruments that measure the total refractive power of the eye while thenatural lens is intact may include contributions to the refractive powerthat are attributable to the natural crystalline lens. Thus, these typesof instruments may not be ideally suited for measurements where only therefractive power attributable to the cornea is sought.

Measurements of the refractive power of the cornea are typicallyobtained using an instrument such as a keratometer or cornealtopographer. Such instruments measure the curvature of the cornealtopographer directly or indirectly. Keratometric data generally includesK values that represent the refractive power of the cornea in orthogonalmeridians that pass through the corneal apex, or anatomical center, ofthe cornea. These values, K1 and K2, can be expressed in terms of theradii of curvature or as the dioptric power of the cornea along theseorthogonal meridians.

The keratometric data may comprise the magnitude of the sphericalrefractive power of the cornea, as well as the magnitude and axis of thecylindrical refractive power of the cornea. The axis of the cylindricalrefractive power can be measured as an angle from a reference meridianon the cornea. For example, the reference meridian may be the 0°-180°horizontal meridian. Once the axis of the cylindrical refractive powerof the cornea is known, a toric IOL implant can be aligned with respectto the axis so as to correct the astigmatism of the cornea. For example,the toric IOL may include an amount of negative refractive power tocompensate for the meridian of the cornea with the greatest amount ofpositive refractive power. In such cases, the toric IOL is properlyaligned when the most negative meridian of the toric IOL coincides withthe most positive meridian of the patient's cornea.

In a typical cataract surgery, the surgeon obtains pre-operativekeratometric data to determine the magnitude of the spherical andcylindrical refractive power of the patient's cornea, as well as theaxis of the cylindrical power. The accuracy of the keratometricmeasurement of the axis of the cylindrical refractive power of thecornea has certain limitations. For example, keratometric measurementsare typically made with respect to the corneal apex. However, ingeneral, the visual axis of the patient's eye is not centered on thecorneal apex. Thus, the magnitude and axis of the cylindrical refractivepower actually experienced by the patient, as measured through thepupil, can be different from the magnitude and axis of the keratometriccylindrical power that is measured with respect to the corneal apex.This difference between the magnitude and axis of cylinder measuredusing a keratometer and the values measured by refraction through thepupil can result in sub-optimal corrective outcomes for cataract surgerypatients.

After obtaining pre-operative keratometric data from the patient'scornea, the surgeon also determines the position at which he or she willmake the phaco incision near the limbus of the cornea. The phacoincision, typically made at 0° or 180° is a small incision through whichthe surgeon removes the patient's natural lens and inserts an IOLimplant. The phaco incision itself induces an amount of cylindricalrefractive power in the cornea. Since keratometric data is generallyobtained pre-operatively, this data does not measure the inducedcylinder that later results from the phaco incision. The magnitude ofinduced cylinder from the phaco incision generally varies from patientto patient. It depends on such factors as age and gender of the patient,as well as patient-specific properties of the eye. (Its axis generallycoincides with the location of the phaco incision.) It is difficult toaccurately predict the amount of induced cylindrical refractive powerfor any given patient. For one patient, a 2.6 mm phaco incision couldinduce 0.25 D of cylinder, while for another it could induce 0.75 D ofcylinder. In both cases, however, the induced cylindrical refractivepower may be assumed to be equal to the 0.5 D average amount of inducedcylinder, or some other predicted value. Any error between the predictedand actual values of the magnitude of induced cylinder can result insub-optimal corrective outcomes for cataract surgery patients.

A toric lens calculator can be used to calculate an estimate of thecorrect magnitude of cylinder for a tonic IOL implant. The tonic lenscalculator also outputs an estimate of the correct axis of orientationof the toric IOL so as to properly correct the patient's cornealastigmatism. The inputs to the toric lens calculator may include thekeratometric measurements of the patient's cornea, including themeasured magnitude and axis of corneal astigmatism, the predictedmagnitude of induced cylinder from the phaco incision, and the angularlocation of the phaco incision. The toric lens calculator calculates themagnitude of cylinder of an IOL implant that will correct the patient'scorneal astigmatism. The tonic lens calculator also calculates theproper axis of orientation for the toric IOL. This information may beobtained using crossed cylinder calculations.

Such calculations compute the cumulative magnitude and axis ofcylindrical refractive power that results from two or more separatecylinder components, each having its own magnitude and axis. Forexample, in the case of cataract surgery where a toric IOL will be used,the magnitude and axis of cylinder of the cornea are measured. Themagnitude and axis of induced cylinder resulting from the phaco incisionare predicted. These two cylinder components are then combined using thecrossed cylinder equation to obtain an estimate of the total magnitudeand axis of cylinder that will be displayed by the cornea after thephaco incision has been made.

The general process for using crossed cylinder calculations to combinethe measured keratometric cylinder with the estimated induced cylinderis as follows:

-   -   Convert cylinder values from polar coordinates to Cartesian        coordinates:        -   Keratometric Corneal Cylinder=Magnitude (Cylc) and Axis (AC)            X _(C)=Cyl_(C)*Cos(2*A _(C))            Y _(C)=Cyl_(C)*Sin(2*A _(C))        -   Induced Cylinder=Estimated Magnitude (Cy and Phaco Incision            Axis (A₁)            X _(I)=Cyl_(I)*Cos(2*A _(I))            Y _(I)=Cyl_(I)*Sin(2*A _(I))    -   The Crossed Cylinder is obtained by adding the Cartesian        coordinates:        X _(N)=(X _(C) +X _(I))        Y _(N)=(Y _(C) +Y _(I))    -   The Cartesian coordinates of the new cylinder are converted back        to polar coordinates as follows:        Cyl_(N)=Square Root((X _(N))²+(Y _(N))²)        A _(N)=Arctan((Y _(N))/(X _(N)))/2        If X _(N)>0 and Y _(N)>0 then, A _(N) =A _(N)        If X _(N)<0, then A _(N) =A _(N)+90        If X _(N)>0 and Y _(N)<0, then A _(N) =A _(N)+180

A toric IOL is selected for the patient based on the output of the toriclens calculator. For example, if a patient's cornea is predicted to have+2.5 D of cylinder after the phaco incision has been made, then a toricIOL with less than or equal to −2.5 D of cylinder can be selected tocorrect or reduce the patient's astigmatism. For example, a tonic IOLwith a magnitude of astigmatic power as close to, but not greater than,−2.5 D can be selected. If a toric lens having exactly the amount ofcylinder necessary to correct the corneal cylinder were to be obtained,and if it were to be inserted into the patient's eye at exactly the axisof the corneal cylinder, then the corneal astigmatism of the patient'seye could in theory be perfectly corrected. However, since toric IOLsare typically only manufactured with a finite number of discretecylinder power values, it may not be possible to choose one thatperfectly cancels the astigmatism of the patient's cornea. If a toricIOL having exactly the magnitude of cylinder necessary to correct thecylinder of the patient's cornea is available, then it is referred to asa fully-correcting IOL. If the magnitude of the cylinder of the toricIOL does not exactly correspond to the magnitude of cylinder of thepatient's cornea, then the tonic IOL is referred to as anon-fully-correcting IOL.

In most cases, a fully-correcting toric IOL is not available. If themagnitude of the toric IOL does not perfectly correspond to themagnitude of the cornea's cylindrical refractive power, then thepatient's eye will exhibit a certain amount of residual astigmatism evenafter the cataract surgery has been performed. Even if afully-correcting IOL is available, there may be some degree of error inthe angular positioning of the toric lens. This misalignment of the IOLalso results in residual astigmatism even if the tonic IOL istheoretically fully-correcting. Misalignment of a tonic IOL can alsoexacerbate the residual astigmatism in the case of anon-fully-correcting toric IOL.

The theoretical residual astigmatism of a fully-correcting toric IOL is,of course, 0.0 D. However, this correction is only obtained if the toricIOL is properly aligned to the axis of the cornea's cylinder. Theresidual astigmatism of a non-fully-correcting toric IOL that isproperly aligned with the corneal cylinder is the difference between themagnitude of cylinder of the cornea and that of the toric IOL. Theresidual astigmatism of a non-fully-correcting toric IOL will be greaterthan this baseline value if the toric IOL is misaligned.

In the past, most residual astigmatism attributable to non-optimalalignment of the toric IOL could be traced to post-surgical rotation ofthe IOL. However, now that improved IOLs are available which generallydo not rotate after the surgery, residual astigmatism is moreattributable to misalignment of the toric lens during the cataractsurgery. While some of this surgical misalignment may be caused bysurgical techniques, it can also be attributable to error in the axiscalculated by the toric lens calculator. In other words, even if it werepossible to always precisely orient the IOL implant at the axisdetermined by the tonic lens calculator, misalignment of the lens wouldstill occur due to errors in the calculated value. As described above,these errors can result from, for example, the fact that the magnitudeof induced astigmatism is unknown and from the fact that keratometricdata is measured with respect to the corneal apex rather than the visualaxis of the patient.

Even small amounts of misalignment of the toric IOL with respect to theaxis of cylinder of the patient's cornea can result in clinicallysignificant increases in the theoretically-attainable residualastigmatism in any given case. This is illustrated by FIGS. 14 and 15.

FIG. 14 is a schematic plan view of a patient's cornea 1400. Supposethat the illustrated cornea 1400 has +2.5 D of cylindrical refractivepower at 80°, as illustrated by the dashed line 1402. Dotted line 1404represents the orientation of a toric IOL implanted within the patient'seye. Suppose that the toric IOL is a non-fully-correcting IOL with −2.06D of cylinder. If the axis of the toric IOL is positioned at 80°, asillustrated in FIG. 14, then the resulting residual astigmatism is 0.44D at 80°.

FIG. 15 illustrates the scenario of a misaligned toric IOL. FIG. 15 is aschematic plan view of a patient's cornea 1500. Suppose that's thecornea 1500 yet again has +2.5 D of cylinder at 80°. This is illustratedby dashed line 1502. Suppose further that the same −2.06 D toric IOL isinserted into the patient's eye, but instead of being oriented at 80°,the toric IOL is oriented 10° counterclockwise at 90°, as represented bydotted line 1504. The residual astigmatism in such a scenario is nolonger +0.44 D. Instead, it is +0.90 D. In addition, one might supposethat the axis of the residual astigmatism would be located between 80°and 90°. However, the axis of the residual astigmatism would actually bemeasured at 54°, as represented by solid line 1506.

If the surgeon were to measure the angular orientation of the toric IOLpostoperatively using a slitlamp microscope, he or she would note thatthe axis of the residual astigmatism is 36° clockwise from the actualorientation of the IOL. As illustrated, a misalignment of the toric IOLby 10° results in a much larger error in the axis of the residualastigmatism. The misalignment of the toric IOL also results in a greatermagnitude of residual astigmatism than the theoretical optimal valuethat would have been obtained if the toric IOL had been properlyoriented.

FIG. 16 is a table 1600 that illustrates the impact of misalignment of atoric IOL on the residual astigmatism for patients having severaldifferent prescriptions. The first prescription in the table 1600corresponds to the one just described with respect to FIGS. 14 and 15.It is a patient with −1.00 D of sphere and +2.50 D of cylinder at 80°. Anon-fully-correcting toric IOL with −2.06 D of cylinder is used for thispatient. The table 1600 illustrates the magnitude and axis of residualastigmatism for cases where the toric IOL is aligned at 100°, 90°, 85°,80°, 75°, 70°, 60°, respectively. The values of the residual astigmatismare given in the “Refraction Measurement” column. Note that amisalignment of only 5° from the 80° axis of corneal cylinder results inthe axis of the residual astigmatism being 19° off from the axis ofcorneal cylinder. Larger misalignments can result in even largerdepartures from the theoretical axis of residual astigmatism using agiven toric IOL. The “Refraction Measurement” column also includes themeasured value of sphere. It can be seen from the table thatmisalignment of the toric IOL not only affects the residual astigmatism(magnitude and axis of cylinder) but also the magnitude of sphericalrefractive power.

Table 1600 also includes example data using the following prescriptions:−0.50+2.00×45°, −0.50+2.00×110°, −1.00+0.60×75°, and −0.75+4.00×90°. Thevalues in the “Refraction Measurement” column of the table 1600 can becalculated using the crossed cylinder equation if the magnitude and axisof both the corneal astigmatism and the toric IOL are known. The columnstitled “Recommended Rotation” and “Measurement Axis Versus Lens Axis”will be described below.

After the surgeon has determined the proper refractive power andorientation of the tonic IOL implant, as described above, he or she mayproceed with the cataract surgery. With the patient in an uprightposition, for example, at a slitlamp microscope, the surgeon may use ahorizontal bubble level to indicate the 0°-180 meridian of the cornea.The surgeon can align a device with angular gradations or graduationmarks, such as a Mendez gauge, to the eye. Then, using the Mendez gauge,the surgeon may mark the limbus of the eye at the angular axiscalculated by the toric IOL calculator. This can be done at the slitlampor later during the surgery. The surgeon will later use this mark toalign the toric IOL to the estimated axis of the corneal astigmatismonce the patient is relocated to a supine surgical position. In someembodiments, the marking of the axis for alignment of the toric IOL, orfor the horizontal or vertical meridian, is done while the patient is inan upright position because the keratometric data used to calculate theestimated axis of the corneal astigmatism after the phaco incision isalso typically measured while the patient is in an upright position. Ifthe tonic IOL axis were marked with the patient in supine positionwithout reference to an axis of the eye marked while the patient was inthe upright position, a clinically significant amount of error could beintroduced due to cyclotorsion of the eye during the transition from theupright to the supine position.

Once an alignment axis, or other reference axis, for the toric IOL ismarked, the patient is placed in a supine surgical position. The surgeonmakes the phaco incision and removes the natural crystalline lens, forexample, by phacoemulsification. Once the natural lens is removed, thesurgeon may fill the capsular bag with visco-elastic material in orderto maintain the form of the capsular bag, and to ease rotation of thetoric IOL within the bag. The surgeon then inserts the toric IOL andaligns its axis using the previously-made mark on the limbus. Thevisco-elastic material is then aspirated from the capsular bag.

In some cases, it can be expected that this aspiration process willcause the IOL to rotate somewhat. Some toric IOLs are designed to rotateeasily in one direction while resisting rotation in the oppositedirection. For example, some IOLs are configured such that the easydirection of rotation is clockwise. Thus, a surgeon may initiallymisalign the toric IOL by a few degrees (i.e., typically less than 10°)counterclockwise from the mark on the limbus in anticipation that thetoric IOL will rotate somewhat clockwise during aspiration of thevisco-elastic material. Once the visco-elastic material has beenaspirated, the surgeon may perform any necessary additional clockwiserotation of the toric IOL until it is aligned with the mark on thelimbus.

The amount of initial misalignment of the toric IOL to account forpossible rotation during aspiration is typically done in the directionopposite from the direction in which the IOL rotates easily. Thus, anyrotation of the IOL during aspiration, which will occur in the directionof easy rotation, will tend to rotate the IOL toward its final positionof alignment. If inadvertent rotation of the IOL during aspiration isexpected, the rotation in the direction opposite from the direction ofeasy rotation should be more than the maximum expected amount ofinadvertent rotation. This helps to avoid the necessity of having tolater rotate the toric IOL against the easy direction of rotation to itsfinal alignment position. However, the initial misalignment tocompensate for rotation during aspiration should not exceed 10° in orderto limit the amount of necessary rotation of the toric IOL after thevisco-elastic material has been removed.

It is often the case in cataract surgeries that the residual astigmatismafter the surgery is not as low as theoretically anticipated. In fact,it has been found during testing of a sample size of 33 cases that theresidual astigmatism in 27% of toric lens outcomes was greater than 0.75D from the theoretically-expected result. As previously mentioned, twopossible causes of these sub-optimal outcomes are as follows: 1) themagnitude and axis of cylinder of the toric IOL are calculated fromkeratometric data, which is measured from the corneal apex rather thanthe center of the pupil; and 2) the keratometric data does not take intoaccount the induced astigmatism that results from the phaco incision;instead, the induced astigmatism is estimated, usually based upon theaverage amount of induced astigmatism across a number of patients.

Each of the foregoing factors can result in the toric IOL beingimproperly aligned with the axis of the cylindrical refractive power ofthe patient's cornea. It is this misalignment that results insub-optimal residual astigmatism. As illustrated by FIG. 16, even smallamounts of alignment error can result in clinically significantincreases ire the residual astigmatism. Thus, it would be beneficial toreduce the impact of the two foregoing factors in order to improvepatient outcomes.

Surgical outcomes could be improved with accurate intra-operativeknowledge of the magnitude and axis of cylindrical refractive power ofthe cornea that is to be corrected by the toric IOL. The magnitude andaxis of the cylinder of the cornea can be accurately calculatedpostoperatively, however. This is done by measuring the total residualastigmatism of the eye postoperatively (i.e., after the eye has healed)and solving the crossed cylinder equation to yield the magnitude andaxis of the corneal cylinder, which was unknown at the time of thesurgery.

As discussed above, the crossed cylinder equation can be used tocalculate an estimate of the residual astigmatism that will result afterimplantation of a toric IOL. This estimate is based on an estimate ofthe magnitude and axis of cylinder attributable solely to the cornea aswell as knowledge of the magnitude and axis of the implanted toric IOL.The accuracy of the estimated residual astigmatism is limited by theaccuracy of the estimate of corneal astigmatism. However, if theresidual astigmatism is measured postoperatively using, for example, awavefront aberrometer, the crossed cylinder equations can be solved todetermine what the magnitude and axis of corneal astigmatism actuallymust have been. Once the true magnitude and axis of corneal astigmatismare known, the crossed cylinder equations can be used to calculate theactual optimal orientation of the toric IOL. If the surgeon deems itworthwhile, a second surgery could be performed to position the toricIOL at this optimal orientation. However, this approach is limited bythe requirement for multiple surgeries as well as the fact that thephaco incision made during the second surgery could once again alter themagnitude and axis of the corneal astigmatism, leading once more tosub-optimal orientation of the toric IOL.

This problem can be solved with the capability to accurately measure thetrue magnitude and axis of the corneal cylinder intra-operatively afterthe phaco incision has been made. This can be done, for example, using awavefront aberrometer mounted to, and optically aligned with, a surgicalmicroscope used by the surgeon to perform the cataract surgery. Such adevice is described in co-pending U.S. patent application Ser. Nos.11/110,653 and 11/110,968, both filed Apr. 20, 2005 and entitled“INTEGRATED SURGICAL MICROSCOPE AND WAVEFRONT SENSOR.” One type ofwavefront aberrometer that is suitable for performing the types ofintra-operative measurements described herein is a Talbot-Moiréwavefront aberrometer such as the ones described in U.S. Pat. No.5,963,300, issued Oct. 5, 1999 and entitled “OCULAR BIOMETER,” and inU.S. Pat. No. 6,736,510, issued May 18, 2004 and entitled “OPHTHALMICTALBOT-MOIRÉ WAVEFRONT SENSOR.” An alignment system for accuratelypositioning a wavefront aberrometer to perform intra-operativemeasurements during cataract surgery is described in co-pending U.S.patent application Ser. No. 12/206,974, filed on Sep. 9, 2008 andentitled “OPTICAL INSTRUMENT ALIGNMENT SYSTEM.” The entire contents ofeach of the foregoing references are hereby incorporated by referenceherein to be considered part of this disclosure.

FIG. 17 illustrates a method 1700 for performing a cataract surgery in amanner that results in more accurate alignment of a toric IOL to theaxis of the patient's corneal astigmatism, thus reducing residualastigmatism and improving the patient's surgical outcome. At block 1702,the surgeon obtains an estimate of the magnitude and axis of thepatient's corneal astigmatism. This estimate can be obtained, forexample, using a keratometer or corneal topographer to obtainkeratometric data. In some embodiments, the keratometric data ismeasured while the patient is in an upright position. As previouslydiscussed, the keratometric data comprises the measured magnitude andaxis of the patient's corneal astigmatism.

In some embodiments, the surgeon may try to improve this keratometricestimate of the cylindrical refractive power of the patient's cornea byestimating the amount of induced astigmatism that will later result fromthe phaco incision. For example, crossed cylinder calculations can beperformed to determine how the estimated induced astigmatism will affectthe measured keratometric axis of the patient's corneal astigmatism.Nevertheless, in some embodiments, the initial orientation of the tonicIOL when inserted in the patient's eye according to the method 1700 neednot be as accurate as in conventional techniques. This is described morefully below. Thus, in some embodiments, it is not necessary to determinethe effect of the estimated induced astigmatism on the measuredkeratometric axis of the patient's corneal astigmatism, and suchcalculations can be omitted.

Once the estimate of the magnitude and axis of the patient's cornealastigmatism is obtained at block 1702 (whether this estimate is basedsolely on keratometric data, or on both keratometric data and anestimate of induced astigmatism), the surgeon may proceed to mark theposition of the axis estimate on the limbus of the patient's eye. Oncemore, however, in some embodiments the initial orientation of the toricIOL according to the method 1700 can have a lower degree of accuracythan may be required when using conventional techniques. Thus, while asurgeon performing a cataract surgery according to method 1700 maychoose to mark the position of the estimated axis of corneal cylinder,in some embodiments such marking is not required and can be foregone. Insome embodiments, any cyclotorsion of the eye that occurs when thepatient is placed in the supine position may not be clinicallysignificant in view of the lax accuracy requirements of the initialorientation of the toric IOL according to method 1700, as described morefully below. Skipping the marking of the limbus with the estimated axisof corneal cylinder can allow for the cataract surgery to be performedmore quickly. The surgery may also be performed more cost-effectivelysince tools that may have been required to make such a mark may nolonger be required.

At block 1704 of method 1700, the surgeon removes the natural lens fromthe patient's eye. At block 1706, the surgeon inserts a toric IOL intothe patient's eye. These steps may involve the introduction ofvisco-elastic material to the capsular bag, as in conventionaltechniques. The actual toric IOL that is used in any given surgery canbe selected, for example, based on the pre-operative keratometricestimate of the magnitude of the patient's corneal astigmatism.

At block 1708, the surgeon deliberately misaligns the axis of the toricIOL by at least 15° from the estimated axis of corneal cylinder. In someembodiments, the misalignment is in the direction opposite from thedirection of easy rotation of the toric IOL. In other embodiments, thesurgeon deliberately misaligns the axis of the tonic IOL by at least 30°in the direction opposite from the direction of easy rotation of thetoric IOL. This deliberate misalignment allows the surgeon to laterrotate the tonic IOL in the direction of easy rotation to obtain thecorrect alignment, as discussed herein. For example, many toric IOLs aremanufactured so as to easily rotate in a clockwise direction. Thus, insome embodiments, the surgeon deliberately misaligns the axis of thetort IOL by at least 15° counterclockwise from the estimated axis ofcorneal cylinder, while in other embodiments the amount of deliberatemisalignment is at least 30° counterclockwise. In the case of a toricIOL that has no preferential direction of rotation, the deliberatemisalignment of the toric IOL can be in either direction from theestimated axis of corneal astigmatism.

In some embodiments, the amount of deliberate misalignment iscounterclockwise by at least 15° but no more than 20°. In someembodiments, the amount of deliberate misalignment is counterclockwiseby at least 20° but no more than 25°. In some embodiments, the amount ofdeliberate misalignment is counterclockwise by at least 25° but no morethan 30°. In some embodiments, the amount of deliberate misalignment iscounterclockwise by at least 30° but no more than 35°. In someembodiments, the amount of deliberate misalignment is counterclockwiseby at least 35° but no more than 40°. In some embodiments, the amount ofdeliberate misalignment is counterclockwise by at least 40° but no morethan 45°. In some embodiments the amount of deliberate misalignment isat least 30°. In some embodiments the amount of deliberate misalignmentis counterclockwise by at least 30° but no more than approximately 90°.It will be understood by those of skill in the art that the deliberatemisalignment will be clockwise from the estimated axis of cornealastigmatism for IOLs having a counterclockwise direction of easyrotation.

Once the toric IOL has been inserted into the capsular bag anddeliberately misaligned with respect to the estimated axis of cornealastigmatism, at block 1710, the total refractive power of the patient'spseudophakic eye (i.e., the eye after implantation of the IOL) isintra-operatively measured while the patient remains in the supinesurgical position. In some embodiments, this intra-operative measurementis performed using, for example, a Talbot-Moiré wavefront aberrometermounted on a surgical microscope, though other systems that measure therefractive properties of the eye could be used (e.g., one incorporatinga Shack-Hartmann wavefront aberrometer).

In some embodiments, the visco-elastic material is aspirated from thecapsular bag prior to the intra-operative measurement of totalrefractive power of the eye so as to reduce any effect that thevisco-elastic material may have on the measurement. For example, thevisco-elastic material may cause the tonic IOL to be tilted somewhat inthe capsular bag such that there is a non-zero angle between the opticalaxis of the IOL and the patient's visual axis. This tilt could impactthe measurement of total refractive power by introducing a tiltcomponent to an intra-operative wavefront measurement. The visco-elasticmaterial could also introduce other first, second, or higher-orderartifacts into the wavefront measurement. In other embodiments, however,the visco-elastic material is left in place during the measurement oftotal refractive power of the eye so as to later facilitate rotation ofthe toric IOL so that its astigmatic axis is aligned to that of thepatient's cornea.

The measurement of the total refractive power of the patient's eyeincludes sphere and cylinder components from both the toric IOL and thepatient's cornea. Crossed cylinder calculations can be performed todetermine the actual magnitude and axis of unknown corneal astigmatismthat, when combined with the known magnitude and axis (which can bemeasured, for example, using the devices described herein) of cylinderof the toric IOL, resulted in the measured composite magnitude and axisof total refractive astigmatism of the cornea/IOL system measuredintra-operatively using, for example, a wavefront sensor.

-   -   Combining measured cylinder with toric lens cylinder:        -   Convert cylinder values from polar coordinates to Cartesian            coordinates using the above equations to yield X_(M), Y_(M),            X_(L) & Y_(L)    -   Calculate “true” corneal cylinder magnitude and axis:        X _(TC)=(X _(M) −X _(L))        Y _(TC)=(Y _(M) −Y _(L))    -   Convert to polar coordinates using the equations above.    -   Required toric lens rotation (described further below) is equal        to        A _(L) −A _(TC)

This calculation can be performed using a computer, whethergeneral-purpose or specialized, a scientific calculator, or some othercomputing device. The computer may be communicatively coupled with awavefront sensor used to perform the intra-operative refractivemeasurements. The computer may comprise a processor, a memory module,and a user interface. In some embodiments, the processor is programmedto calculate the actual magnitude and axis of corneal astigmatism basedon input information comprising the intra-operatively measured magnitudeand axis of total refractive cylinder and the known magnitude and axisof cylinder of the toric IOL. The processor may, store for example, thecalculated actual magnitude and axis of corneal astigmatism in thememory module. In addition, the processor may output the actual cornealastigmatism values to the surgeon using the user interface. The userinterface may also allow for the surgeon to input information such as,for example, the keratometric measurements of a patient's eye, themodel, sphere, and cylinder of a selected toric IOL, etc. In someembodiments, the user interface provides the surgeon with prompts thathelp to guide the surgery.

In some embodiments, the computer is communicatively coupled to arepository of information (e.g., a central database) by, for example, acomputer network (e.g., the internet). The repository of information mayinclude information about available IOLs to help the surgeon make aselection of a suitable IOL for use in a patient's surgery. The computermay also upload information comprising the measurements of a patient'saphakic, or pseudophakic, eye to the repository of information. Thisinformation can be collected and made available for analysis, forexample, by other surgeons or researchers. In some embodiments, thecollection of aphakic or pseudophakic measurements made by a particularsurgeon can be analyzed to determine surgeon-specific corrective factorsthat can be applied to improve that surgeon's results in the future. Forexample, if a particular surgeon has a demonstrated tendency, based onthe collected measurements, to achieve outcomes that are 0.5 D worsethan the theoretically-achievable result, than appropriate correctionscan be made for that surgeon's future patients with regard to toric IOLselection, calculation of corneal cylinder, etc.

With reference to FIG. 16, the foregoing calculation is used todetermine the information in the “Corneal Refraction” column, which isunknown, from the information in the “Toric Lens Power and Axis” columnand the “Refraction Measurement” column. FIG. 16 also includes a“Recommended Rotation” column and a “Measurement Axis Versus Lens Axis”column. The “Measurement Axis Versus Lens Axis” column contains anglesthat are representative of the difference between the axis of actualmeasured total refraction and the axis of orientation of the toric IOL.The “Recommended Rotation” column includes angles which represent theamount of angular rotation which should be imparted to the toric IOL inorder to properly align it with the axis of corneal cylinder that isdetermined using the foregoing calculation. In some embodiments, theprocessor that calculates the actual magnitude and axis of cornealastigmatism can also be used to calculate the amount by which the toricIOL should be rotated to achieve proper orientation for correcting thecorneal astigmatism. This value can be outputted to the surgeon by wayof the user interface. In some embodiments, this recommended rotationvalue typically has a magnitude in the range of the amount of deliberateinitial misalignment ±10°. The recommended rotation will typically be inthe direction opposite from the direction of initial misalignment (e.g.,clockwise). The ±10° may be due to any error in the initial estimate ofthe astigmatic axis of the cornea.

The intra-operative measurements of total refractive power do not sufferfrom the same defects as the pre-operative keratometric measurements andinduced astigmatism estimates described herein. Namely, the totalrefractive intra-operative measurements can be performed using, forexample, a wavefront aberrometer that measures refraction of the eyethrough the pupil. As described herein, keratometric data typically istaken with respect to the corneal apex, which does not necessarilycoincide with the visual axis of the patient, resulting in differentastigmatic measurements than those performed through the pupil. Inaddition, the intra-operative measurements of total refractive power areperformed after the phaco incision has been made. Thus, theseintra-operative measurements remove the guesswork involved in estimatingthe induced astigmatism that results from the phaco incision.

There are at least two advantages to deliberately misaligning the toricIOL prior to the intra-operative measurement of total refractive powerof the eye, in some embodiments. First, if the toric IOL is initiallymisaligned by a sufficient angular amount in the counterclockwisedirection (e.g., at least 15° in some embodiments, or at least 30° inother embodiments), then there is a low likelihood of having to make a,for example, counterclockwise rotation of the toric IOL afterintra-operative measurements have been performed to determine the trueaxis of corneal astigmatism. This is beneficial because many toric IOLsare designed to only rotate easily in the clockwise direction. Ofcourse, if a given toric IOL is designed to rotate easily in thecounterclockwise direction, then the initial misalignment would bebiased toward the clockwise direction.

In addition, the wavefront aberrometer described herein is capable ofmeasuring the axis of astigmatism more accurately when an appreciableamount of astigmatism is present then in the case where very littleastigmatism is present. Thus, within limits, the greater the magnitudeof astigmatism present in the eye after the toric IOL is initiallyinserted in a misaligned state, the more accurately the wavefrontaberrometer used to perform the intra-operative measurements of totalrefractive power of the eye can determine the axis of the astigmatism.If the toric IOL were initially misaligned by, for example, less than15°, the magnitude of the residual astigmatism resulting from thismisalignment may not be great enough in some cases to accurately measurethe axis of that astigmatism. If, instead, the toric IOL is initiallymisaligned by greater than 15°, or by greater than 30°, then it is morelikely that the axis of total refractive astigmatism can be accuratelymeasured. This is important because the ultimate post-surgical residualastigmatism can only be reduced or minimized if the axis of cornealastigmatism can be accurately determined.

The amount of deliberate misalignment of the toric IOL performed atblock 1708 of method 1700 is greater, possibly much greater, than anydeliberate misalignment that a surgeon may employ in anticipation ofinadvertent rotation of the toric IOL during aspiration of thevisco-elastic material according to conventional techniques. In the caseof the former, the amount of deliberate misalignment is intended to belarge enough to avoid having to make a counterclockwise rotation of thetoric IOL once the correct axis of the corneal astigmatism is known,whereas in the case of the latter it is assumed that the correct axis ofthe corneal astigmatism has been accurately estimated and the deliberatemisalignment is only intended to compensate for any inadvertent rotationof the IOL which may occur during aspiration of the visco-elasticmaterial from the capsular bag. In fact, in some embodiments, the lattertechnique of deliberately misaligning the toric IOL in anticipation ofan inadvertent rotation during aspiration can be used in combinationwith the technique of block 1708.

As described herein, the techniques according to method 1700 allow thesurgeon to initially insert the IOL at a somewhat arbitrary orientationrather than trying to accurately estimate the actual axis of cornealastigmatism (e.g., the surgeon does not necessarily have to attempt tocorrect the pre-operatively-measured keratometric astigmatic axis withan estimate of the induced astigmatism). Nor does the surgeonnecessarily have to mark the position of the keratometric astigmaticaxis pre-operatively while the patient is in an upright position. Thetoric IOL can be somewhat arbitrarily placed so long as this arbitraryorientation provides an adequate buffer against the possible need forcounterclockwise rotations that may result from not previously havingfully or partially considered or compensated for the following effects:the effect of induced astigmatism resulting from the phaco incision; theeffect of cyclotorsion when the patient is moved to the supine position;and/or not having made an alignment mark on the limbus that correspondsto the estimated axis of corneal astigmatism, the alignment mark servingas a reference point from which to judge the amount of initialdeliberate misalignment of the IOL.

Once the true magnitude and axis of corneal astigmatism have beendetermined (block 1712) based at least in part upon theintra-operatively measured total refractive power of the eye, the toricIOL can be rotated, at block 1714, from its deliberately misalignedstate to proper alignment with the axis of the patient's cornealastigmatism. Once again, the amount and direction of necessary rotationof the toric IOL relative to the initial misaligned orientation can bedetermined by calculating the difference between the known misalignedaxis of the toric IOL and the calculated axis of the patient's cornealcylinder, as indicated in the “Recommended Rotation” column of table1600 in FIG. 16. This rotation value can be outputted to the surgeon,who can then use an instrument such as a Mendez gauge to make the properamount of relative rotation. Once the toric IOL has been rotated to thecorrect axis of the patient's corneal astigmatism, the remainder of thecataract surgery can be performed conventionally. Another pseudophakicmeasurement can also be performed to check the accuracy of the alignmentof the toric IOL.

In some embodiments, the necessary amount of rotation of the toric IOLfrom the misaligned state to one that is aligned with the calculatedaxis of corneal astigmatism is performed using a system that, forexample, comprises a refractive measurement instrument that is mountedto and may be optically aligned with the surgical microscope being usedto perform the cataract surgery. In some embodiments, the refractivemeasurement instrument is a wavefront aberrometer. Embodiments of aTalbot-Moiré wavefront aberrometer mounted to, and optically alignedwith, the surgical microscope are described herein. The system forperforming the necessary rotation of the toric IOL can also include anintegrated module for providing an indicia to the surgeon of the axis towhich the toric IOL should be aligned.

In some embodiments, this indicia is provided by any one of the opticalangular measurement systems described herein. For example, the indiciacan be provided by an optical system that projects a line or otheralignment indicia onto the patient's eye that indicates the axis towhich the toric IOL should be rotated, as described herein. For example,in some embodiments, a laser line is projected on the patient's eye thatindicates this axis.

FIG. 18 illustrates another embodiment where a method 1800 is used toaccurately orient a toric IOL by intra-operatively measuring therefractive power of the aphakic eye. It should be understood by those ofskill in the art that the aphakic and pseudophakic measurementsdescribed herein could be performed not only by a Talbot-Moiré wavefrontaberrometer mounted to a surgical microscope, as described herein, butalso by any other type of wavefront aberrometer, whether mounted to thesurgical microscope or not. Other types of measurement devices, such asautorefractors, could also be used. In addition, handheld devices formeasuring refractive power of the patient's eye can be used. The method1800 begins at block 1802 where the surgeon removes the patient'snatural lens through a phaco incision. Once the natural lens has beenremoved, at block 1804, the surgeon uses an ophthalmic instrument, forexample as described herein, to perform an intra-operative measurementof the refractive power of the patient's aphakic eye. Since thepatient's natural lens has already been removed at this point, themeasured refractive power is attributable substantially only to thecornea. This measurement is taken through the pupil after the phacoincision has already been made. Thus, it does not suffer from theweaknesses of the pre-operative keratometric measurements describedherein.

At block 1806, the magnitude and axis of astigmatism attributable to thecornea are determined using the aphakic intra-operative wavefrontrefractive measurements. A computer communicatively coupled to theinstrument for performing this aphakic measurement can also becommunicatively coupled with a database of available toric IOLs. Afterthe aphakic measurement, this database can be electronically consultedto provide a recommendation to the surgeon of a suitable IOL to be used.At block 1808, the surgeon inserts the selected toric IOL. At block1810, the surgeon rotates the toric IOL to align its axis with the axisof the patient's corneal astigmatism. Other aspects of the surgery canbe performed conventionally.

In some embodiments, once the toric IOL has been inserted androtationally oriented based upon the aphakic measurement of therefractive power of the patient's eye, an intraoperative pseudophakicmeasurement can be performed in order to determine the accuracy withwhich the toric IOL has been angularly aligned. For example, the totalcylindrical power and axis of the patient's pseudophakic eye can bedetermined. The values of the cylindrical power and axis can then beused to determine whether the toric IOL is properly aligned. Forexample, if the toric IOL is theoretically fully-correcting and properlyaligned, then the cylindrical power of the pseudophakic eye should besubstantially 0.0 diopters. If the theoretically fully-correcting toricIOL results in an unexpected amount of residual astigmatism in thepseudophakic eye, then the crossed cylinder equations described hereincan be used to back calculate the direction and amount by which thetoric IOL should be rotated in order to achieve improved astigmaticcorrection.

For example, based on the inputs of the cylindrical power and axis ofthe aphakic eye, and on the cylindrical power and axis of thepseudophakic eye, the crossed cylinder equations can be used todetermine the actual angular orientation of the tonic IOL that wasinserted into the eye (as well as confirming the astigmatic power of thetoric IOL). These values can be used to determine whether residualastigmatism can be reduced by an adjustment to, for example, the angularorientation of the toric IOL (or possibly by substituting a toric IOLwith a different amount of cylindrical power). For example, thedirection and amount by which the toric IOL should be rotated to reduceresidual astigmatism, if any, can be determined by calculating thedifference between the calculated angular orientation of the toric IOLand the intended angular orientation that was determined based on theaphakic measurement. A computer can perform these calculations andoutput, for example, the direction and amount by which the toric IOLshould be rotated.

If the toric IOL is non-fully-correcting, then the cylindrical power andaxis values obtained from the pseudophakic measurement can be comparedto the theoretically expected values of residual astigmatism, which canbe obtained, for example, by using the crossed cylinder equations todetermine the expected cylindrical power and axis resulting from thecombination of the aphakic measurement of cylindrical power and axiswith the known cylindrical power and intended axis of the toric IOL. Ifthe measured cylindrical power and axis of the pseudophakic eye differsfrom the theoretically expected residual astigmatism values, then thepseudophakic measurements can be used to determine the direction andamount by which the toric IOL should be rotated in order to improve theresidual astigmatism. For example, the crossed cylinder equations can beused to back calculate the direction and amount by which the tonic IOLshould be rotated, as described herein. These values can then be outputto, for example, the surgeon. In this way, a pseudophakic measurementcan be used to improve surgical outcomes even when an aphakicmeasurement is used to determine the angular axis to which a toric IOLshould be aligned.

FIG. 19 illustrates another embodiment where a method 1900 is used toaccurately orient a toric IOL by performing at least two intra-operativerefractive measurements of the pseudophakic eye while a tonic IOL ispositioned at two distinct angular orientations. The method 1900 beginsat block 1902 where the surgeon removes the patient's naturalcrystalline lens from the eye. In some embodiments, the surgeon may havealready obtained an estimate of the axis of the patient's cornealastigmatism using, for example, keratometric data. Next, at block 1904,the surgeon inserts a toric IOL at a first angular orientation. Thefirst angular orientation is arbitrary in some embodiments. However, insome embodiments, the first angular orientation is at least 15° from theestimated axis of the patient's corneal astigmatism. At block 1906, thesurgeon intra-operatively measures the total refractive power of thepatient's pseudophakic eye (the eye after the IOL has been implanted).

Next, the surgeon rotates the toric IOL to a second angular orientation(block 1908) distinct from the first. In some embodiments, the secondangular orientation is separated from the first by an arbitrary, butknown, amount. The amount and direction of angular separation betweenthe first and second angular orientations can be measured using, forexample, a Mendez gauge, or an angular measurement or tracking systemintegrated with the optical instrument for intra-operatively measuringthe total refractive power of the patients pseudophakic eye, asdescribed herein. Other methods and/or instruments for measuring thedifference between the first and second angular orientations are alsopossible.

In some embodiments the second angular orientation is separated from thefirst by at least 15°. In some embodiments, the second angularorientation may also be separated from the estimated axis of cornealastigmatism by at least 15°. Once the tonic IOL is positioned at thesecond angular orientation, at block 1910, the surgeon once againintra-operatively measures the total refractive power of thepseudophakic eye. The previously-described computer may be programmedwith software that provides, for example, prompts or other informationto help guide the surgeon through the process of determining when toperform a refractive power measurement, when, and by how much, to rotatethe toric IOL from the first angular orientation to the second, etc.

Using the crossed cylinder equation and the measurements of themagnitude and axis of astigmatism of the pseudophakic eye at twodistinct positions, a system of equations comprising two equations withtwo unknowns can be formed. For example, in some embodiments, theresulting mathematical relationship is a sine squared relationship. Atblock 1912, the system of equations can be solved to determine themagnitude and axis of corneal astigmatism which, when combined with theknown magnitude and axis of the toric IOL at the two distinct positions,resulted in the measured total astigmatic refractive values of thepatients pseudophakic eye at those two distinct positions. Finally, atblock 1914, the surgeon can rotate the toric IOL to the correct axiswhich corresponds to the calculated astigmatic axis of the patient'scornea. The computer can calculate the amount and direction of thisrotation, for example, by determining the difference between the secondangular orientation of the toric IOL and the corneal astigmatic axiscalculated from the system of equations.

It will be understood by those of skill in the art that, while certainprocedures have been disclosed herein, these procedures can be alteredand adapted, for example, depending upon the type of toric IOL used in agiven cataract surgery, the available surgical equipment, the skill andcustomary techniques of the surgeon, the needs of the patient's, andother factors known to those of skill in the art. These alterations andadaptations can be made without departing from the scope of theinvention. In addition, it should be appreciated that the steps ofmethods described herein can be reordered, and some steps may beomitted, in many instances.

The systems and methods described herein can advantageously beimplemented using, for example, computer software, hardware, firmware,or any combination of software, hardware, and firmware. Software modulescan comprise computer executable code for performing the functionsdescribed herein. In some embodiments, computer-executable code isexecuted by one or more general purpose computers. However, a skilledartisan will appreciate, in light of this disclosure, that any modulethat can be implemented using software to be executed on a generalpurpose computer can also be implemented using a different combinationof hardware, software, or firmware. For example, such a module can beimplemented completely in hardware using a combination of integratedcircuits. Alternatively or additionally, such a module can beimplemented completely or partially using specialized computers designedto perform the particular functions described herein rather than bygeneral purpose computers. In addition, where methods are described thatare, or could be, at least in part carried out by computer software, itshould be understood that such methods can be provided oncomputer-readable media (e.g., optical disks such as CDs or DVDs, harddisk drives, flash memories, diskettes, or the like) that, when read bya computer or other processing device, cause it to carry out the method.

A skilled artisan will also appreciate, in light of this disclosure,that multiple distributed computing devices can be substituted for anyone computing device illustrated herein. In such distributedembodiments, the functions of the one computing device are distributedsuch that some functions are performed on each of the distributedcomputing devices.

Embodiments have been described in connection with the accompanyingdrawings. However, it should be understood that the figures are notdrawn to scale. Distances, angles, etc. are merely illustrative and donot necessarily bear an exact relationship to actual dimensions andlayout of the devices illustrated. In addition, the foregoingembodiments have been described at a level of detail to allow one ofordinary skill in the art to make and use the devices, systems, etc.described herein. A wide variety of variation is possible. Components,and/or elements may be altered, added, removed, or rearranged in waysthat will be appreciated by those of ordinary skill in the art. Whilecertain embodiments have been explicitly described, other embodimentswill become apparent to those of ordinary skill in the art based on thisdisclosure.

What is claimed is:
 1. An ophthalmic system, comprising: an opticalrefractive power measurement device, configured to be integrated with asurgical microscope, for intraoperatively measuring at least thecylindrical power and axis of a patient's eye, wherein the patient's eyeis aphakic or pseudophakic; and an optical angular measurement deviceconfigured to be integrated with the surgical microscope or the opticalrefractive power measurement device, the optical angular measurementdevice being configured to provide at least one angular indicator forintraoperatively performing angular measurements or alignments withrespect to the patient's eye, wherein the optical angular measurementdevice is configured to provide the at least one angular indicator withrespect to measurement axes that are consistent with those of theoptical refractive power measurement device.
 2. The ophthalmic system ofclaim 1, wherein the angular indicia comprises a graphical pattern withangular graduation marks.
 3. The ophthalmic system of claim 2, whereinthe angular graduation marks are formed at intervals of at least every5°.
 4. The ophthalmic system of claim 1, wherein the at least oneangular indicator comprises a movable indicator at a determined angularposition for performing a surgical action.
 5. The ophthalmic system ofclaim 1, wherein the at least one angular indicator comprises indicia ofvertical and horizontal meridians, and wherein the optical refractivepower measurement device and the optical angular measurement device arefixedly mounted such that the indicia of vertical and horizontalmeridians are aligned with vertical and horizontal axes of the opticalrefractive power measurement device.
 6. The ophthalmic system of claim1, wherein the at least one angular indicator is projected onto thepatient's eye.
 7. The ophthalmic system of claim 1, wherein the at leastone angular indicator is superimposed upon a view of the patient's eye.8. An ophthalmic system, comprising: an optical refractive powermeasurement device, configured to be integrated with a surgicalmicroscope, for intraoperatively measuring at least the cylindricalpower and axis of a patient's eye; and an optical angular measurementdevice configured to be integrated with the surgical microscope or theoptical refractive power measurement device, the optical angularmeasurement device being configured to provide at least one angularindicator for intraoperatively performing angular measurements oralignments with respect to the patient's eye, wherein the opticalangular measurement device is configured to provide the at least oneangular indicator with respect to measurement axes that are consistentwith those of the optical refractive power measurement device, whereinthe optical angular measurement device comprises: a reticle, the reticlecomprising a plurality of angular graduation marks; and a light sourcefor illuminating the reticle.
 9. The ophthalmic system of claim 8,wherein the optical refractive power measurement device has a firstoptical pathway along a first optical axis, and the optical angularmeasurement device has a second optical pathway along a second opticalaxis, and wherein the surgical microscope is for viewing the patient'seye via a third optical pathway along a third optical axis during asurgical procedure, and further comprising a combining optical elementfor combining at least a portion of the second optical pathway with thethird optical pathway.
 10. The ophthalmic system of claim 9, wherein thesecond optical pathway and the third optical pathway are combined suchthat the at least one angular indicator is superimposed upon a viewprovided by the surgical microscope.
 11. The ophthalmic system of claim9, wherein the length of the second optical pathway from the reticle tothe surgical microscope is substantially equal to the length of thethird optical pathway from the surgical microscope to the patient's eyewhen the ophthalmic system is located at a predetermined workingdistance above the patient's eye.
 12. The ophthalmic system of claim 9,wherein the reticle is located at substantially the same apparentdistance from the surgical microscope as a patient's eye when theophthalmic system is located at a predetermined working distance fromthe patient's eye.
 13. The ophthalmic system of claim 9, wherein thereticle is located at an object plane of the surgical microscope. 14.The ophthalmic system of claim 9, wherein the optical refractive powermeasurement device comprises a separate housing having a fastener forremovably attaching the optical refractive power measurement device tothe surgical microscope, the housing having an optical pathwaytherethrough for passing visible light from the patient's eye to thesurgical microscope, the combining optical element being located alongthe optical pathway.
 15. The ophthalmic system of claim 9, wherein thecombining optical element is configured such that the first and thirdoptical axes are collinear along at least a portion thereof.
 16. Theophthalmic system of claim 9, wherein the combining optical element isconfigured such that the second and third optical axes are collinearalong at least a portion thereof.
 17. The ophthalmic system of claim 9,wherein the combining optical element is configured such that the firstand second optical axes are collinear along at least a portion thereof.18. The ophthalmic system of claim 9, wherein the combining opticalelement is configured such that the first, second, and third opticalaxes are collinear along at least a portion thereof.
 19. The ophthalmicsystems of claim 9, wherein the optical refractive power measurementdevice and the optical angular measurement device are arranged withrespect to one another such that the first and second optical axes areangularly separated but intersect at a predetermined working distancefrom the ophthalmic surgical device.
 20. The ophthalmic system of claim19, wherein the optical angular measurement device comprises a lens forimaging the reticle onto the patient's eye.
 21. The ophthalmic system ofclaim 9, wherein the surgical microscope comprises a stereoscopicsurgical microscope and has a support structure for movably supportingthe surgical microscope over a supine patient.
 22. The ophthalmic systemof claim 9, wherein the at least one angular indicator is switchablebetween on and off states without disabling the view provided by thesurgical microscope.
 23. The ophthalmic system of claim 8, wherein thereticle comprises an opaque material and the angular graduation markscomprise optically transmissive regions formed in the opaque material.24. The ophthalmic system of claim 8, wherein the reticle comprises apattern of opaque regions surrounded by air or in optically transmissivematerial.
 25. The ophthalmic system of claim 8, wherein the reticlecomprises an alignment mark that is distinguished from the angulargraduation marks.
 26. The ophthalmic system of claim 24, wherein thealignment mark is rotatable.
 27. The ophthalmic system of claim 8,wherein the optical refractive power measurement device comprises awavefront aberrometer.
 28. The ophthalmic system of claim 8, wherein theoptical angular measurement device comprises a scanning light beam forcreating the at least one angular indicator.
 29. The ophthalmic systemof claim 8, further comprising a computer configured to determine anangular alignment value based upon a measurement from the opticalrefractive power measurement device.
 30. The ophthalmic system of claim28, wherein the angular alignment value comprises the angularorientation to which a toric intraocular lens should be aligned based atleast upon an aphakic or pseudophakic measurement of the patient's eye.31. The ophthalmic system of claim 28, wherein the angular alignmentvalue comprises the angular orientation at which an incision should bemade in the patient's eye.
 32. The ophthalmic system of claim 28,wherein the angular alignment value comprises the angular orientation towhich a surgical implant should be aligned.
 33. The ophthalmic system ofclaim 28, wherein the computer is configured to adjust the at least oneangular indicator based on the angular alignment value.
 34. Theophthalmic system of claim 8, wherein the optical angular measurementdevice comprises a computer controllable spatial light modulator. 35.The ophthalmic system of claim 8, wherein the optical angularmeasurement device comprises a holographic element for creating the atleast one angular indicator.
 36. The ophthalmic system of claim 8,wherein the optical angular measurement device comprises a spinningmirror for creating the at least one angular indicator.
 37. Theophthalmic system of claim 8, wherein the optical angular measurementdevice comprises an acousto-optic modulator for creating the at leastone angular indicator.
 38. The ophthalmic system of claim 8, wherein theoptical angular measurement device comprises an electro-optic modulatorfor creating the at least one angular indicator.